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560 



U. S. DEPARTMENT OF AGRICULTURE. 

OFFICK OF EXPERIMENT STATIONS— BULLETIN NO. 126. 

A. C. TRUE. Director. 



STUDIES ON THE DIGESTIBILITY AND 
NUTRITIVE VALUE OF BREAD 



THE UNIVERSITY OF MINNESOTA 



1 9 O O — 1 9 O 2 . 



HARRY SNYDER, B. S., 

Professor of Chemistry, ''allege of Agriculture. University of Minnesota, and 
Chemist, Agricultural Experiment Station. 




WASHINGTON: 

GOV E R X M E X T P R I X T I X ("J- O F F I 0* E . 

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554 



U. S. DEPARTMENT OF AGRICULTURE. 

OFFICE OF EXPERIMENT STATIONS— BULLETIN NO. 126. 

A. C. TRUE, Director. 



3'7--0 



STUDIES ON THE DIGESTIBILITY AND 
NUTRITIVE VALUE OF BREAD 



THE UNIVERSITY OF MINNESOTA 



1900-1902. 



HARRY SNYDER, B. S., 

Professor of Chemistry, College of Agriculture, University of Minnesota, and 
Chemist, Agricultural Experiment Station. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE 

1903. 



t< 



&, 






OFFICE OF EXPERIMENT STATIONS. 

A. C. True, Ph. D., Director. 

E. W. Allen, Ph. D., Assistant Director and Editor of Experiment Station Record. 
C. F. Langworthy, Ph. D., Editor and Expert on Foods and Animal Production. 

NUTRITION INVESTIGATIONS. 

W. O. Atwater, Ph. D., Chief of Nutrition Investigations, Middletown, Conn. 
C. D. Woods, B. S., Special Agent at Orono, Me. 

F. G. Benedict, Ph. D., Physiological Chemist, Middletown, Conn. 
R. D. Milner, Ph. B., Editorial Assistant, Middletown, Conn. 

2 



LETTER OF TRANSMITTAL 



IT. S. Department of Agriculture, 
Office of Experiment Stations, 

Washington, D. C. , February 15, 1903. 
Sir: I have the honor to transmit herewith, and to recommend for 
publication as a bulletin of this Office, a report of investigations on 
the digestibility and nutritive value of bread carried on at the Uni- 
versity of Minnesota in 1900-1902 by Harry Snyder, professor of 
chemistry in the State university and chemist of the agricultural 
experiment station. The studies were conducted under the imme- 
diate supervision of Prof. W. O. Atwater, chief of nutrition investi- 
gations, and Prof. Charles D. Woods, and form a part of the investi- 
gations on food of man conducted under the auspices of this Office. 
Thanks are due the Northwestern Consolidated Milling Company, of 
Minneapolis, Minn., for specially grinding samples of hard wheat, 
and to the Goshen Milling Company, of Goshen, Ind., and the Christian 
Breisch Milling Company, of North Lansing, Mich., for similar favors 
with respect to soft wheat. 

The results of these investigations are in accord with those obtained 
in former studies, and indicate that fine patent flours from both hard 
and soft wheat are more digestible than corresponding coarse flours, 
though they contain somewhat less protein and mineral matter pound 
for pound. The investigations also show that all flours are quite 
thoroughly digested, and furnish experimental proof of the generally 
recognized fact that wheat flours of all grades are among the most 
important articles of diet. 

Respectfully, A. C. True, 

Director. 
Hon. James Wilson, 

Secretary of Agriculture. 



CONTENTS. 



Page. 

Introduction 7 

Methods of sampling and analysis - 8 

Description of samples of food materials 10 

Composition of samples of food materials 12 

Composition of feces and urine obtained in digestion experiments 17 

Experimental methods 18 

Details of the digestion experiments with bread from different grades of hard 

spring wheat flour 20 

Digestion experiment No. 242 21 

Digestion experiment No. 243 ' 22 

Digestion experiment No. 244 23 

Digestion experiment No. 245 23 

Digestion experiment No. 246 24 

Digestion experiment No. 247 25 

Digestion experiment No. 248 26 

Digestion experiment No. 249 26 

Digestion experiment No. 250 27 

Summary of results obtained with hard spring wheat products 28 

Details of the digestion experiments with bread from different grades of soft 

winter wheat flour 32 

Digestion experiment No. 309 32 

Digestion experiment No. 310 33 

Digestion experiment No. 311 34 

Digestion experiment No. 312 35 

Digestion experiment No. 313 35 

Digestion experiment No. 314 36 

Digestion experiment No. 315 37 

Digestion experiment No. 316 38 

Digestion experiment No. 317 38 

Digestion experiment No. 318 39 

Digestion experiment No. 319 40 

Digestion experiment No. 320 41 

Digestion experiment No. 321 41 

Digestion experiment No. 322 42 

Digestion experiment No. 323 43 

Summary of results obtained with soft winter wheat products 44 

General summary of results and conclusions 50 

5 



ILLUSTRATIONS. 

Page. 
Plate I. Fig. 1. — Flour particles from straight patent flour No. 240. Fig. 2. — 

Flour particles from entire- wheat flour No. 241 48 

II. Fig. 1. — Flour particles from graham flour No. 243. Fig. 2. — Feces 

from bread from straight patent flour 48 

III. Fig. 1. — Feces from bread made from graham flour. Fig. 2. — Feces 

from bread made from entire-wheat flour 48 

6 



STUDIES ON THE DIGESTIBILITY AND NUTRITIVE 
VALUE OE BREAD. 



INTRODUCTION. 

The investigations reported in this bulletin, which were carried on at 
the University of Minnesota in 1900-1902, are a continuation of the 
experiments on the digestibility and comparative nutritive value of 
bread made from different grades of flour reported in previous bulle- 
tins of this Office, a and include two series of digestion and nitrogen 
metabolism experiments with healthy men on a diet of milk and bread 
made from different grades of wheat flour, namely, straight patent, 
entire wheat, and graham. In the first series, which included 9 
experiments carried on in 1900-1901 (pp. 20-31), the different grades of 
flour used were all ground from the same lot of hard Scotch Fife spring 
wheat. In the second series, which included 15 experiments, carried 
on in 1901-2 (pp. 32-50), the flours were ground from soft winter wheat. 

The standard grades of flour produced by the modern process of 
milling are discussed in detail in a former bulletin b and also in later 
pages of this bulletin. Briefly stated, by graham flour is meant the 
product obtained by grinding the entire wheat kernel. Entire-wheat 
flour is the product obtained b} 7 removing about one-half of the coarse 
bran before grinding. This flour is finer than graham, but not as fine 
as the patent grades of flour. In milling the patent flour all of the 
bran is removed. Several grades of patent flour are produced, but 
the one most commonly found on the market, known as "standard 
patent," "straight patent," or "straight grade" consists of the first 
and second patent and first clear grades combined. By ordinary proc- 
esses of milling a little over 72 per cent of the total wheat is recovered 
as straight or standard patent flour and about 2.5 per cent as low grade 
and "red dog" flours, the remaining 25 percent being returned in the 
form of bran, shorts, and other offal. 

During late } r ears the relative food value and merits of these differ- 
ent kinds of flour have been the subject of extensive discussion; but 
an examination of the literature on bread and flour shows that but few 
digestion experiments which are really directly comparable have been 

«U. S. Dept. Agr., Office of Experiment Stations Buls. 67 and 101. 
&U. S. Dept. Agr., Office of Experiment Stations Bui. 101, pp. 7, 8. 



8 

made with the different kinds of flour. Wheat ranges in protein con- 
tent from about 11 to 17 per cent; therefore, in order that the results of 
experiments may be comparable, the three kinds of flour should be 
milled from the same lot of wheat. In the former report it was shown 
that when the three different kinds of flour were ground from the same 
lot of hard spring wheat the graham and entire-wheat flours contained 
a little more protein and gave a slightly higher fuel value than the 
straight patent flour; but the coarser graham and en tire- wheat flours 
had a lower coefficient of digestibility than the finer straight patent 
flour. Hence the straight patent flour furnished the body more 
nutritive material per gram or per pound than either the graham or 
entire-wheat flour. Because of the importance of the subject and the 
extensive use of wheat as a human food it was .deemed desirable to 
repeat the work, and in so doing to extend the periods of the digestion 
experiments over a longer time than in the case of the experiments 
previously reported, in which they were only two days each. The 
experiments of 1900-1901 were therefore practically a repetition of 
those of 1899-1900, except that the digestion period in each case was 
twice as long, i. e., four days. 

In 1901-2 experiments were made similar to those of 1900-1901, but 
with soft winter wheat, which is somewhat different in character from 
the hard spring wheat, in order to determine whether the results would 
be the same with flours ground from different sorts of wheat. 

In connection with both series of experiments a number of analyses 
were made of the varieties of wheat studied and of their milling products 
as well as of the milk which formed a part of the diet in the digestion 
experiments. The necessary analyses were also made of the feces and 
urine to secure data for use in computing the digestibility of the food 
and the balance of income and outgo of nitrogen. 

METHODS OF SAMPLING AND ANALYSIS. 

The analytical methods employed in these investigations were prac- 
tically those recommended by the Association of Official Agricultural 
Chemists/' a few modifications suggested by experience being intro- 
duced. 

A sample of each loaf of bread used during the separate digestion 
experiments was analyzed. One hundred grams of bread was reserved 
for the dry matter determination, and proportional parts of the dry 
matter of the bread from various loaves were united to form a com- 
posite sample, which contained a part of each loaf of bread propor- 
tioned to the size and moisture content of the loaf. 

A composite sample was made of the milk in the experiments of 
1900-1901 by saving, in a bottle containing 100 milligrams of potas- 

«U. S. Dept. Agr., Division of Chemistry Bui. 46, revised. 



9 

sium bichromate, 25 cubic centimeters of the milk used at each meal. 
In the experiments of 1901-2 the amount of milk reserved at each 
meal was 50 cubic centimeters. The temperature of the drying oven 
was kept at about 60° C. in all cases of the determination of moisture 
in the feces. The bread was also dried at this temperature. Nitrogen 
was determined by the ordinary Kjeldahl process. In the case of 
wheat and its milling products and bread, protein was obtained by 
multiplying nitrogen by the factor 5.7. In the case of protein in the 
milk and the feces the factor used was 6.25. No attempt was made to 
separate and determine the amount of metabolic nitrogen of the feces. 
Carefully purified ether was used for determining ether extract in 
the bread and feces. The results obtained for the fat in the feces 
were not satisfactory in many cases, although the determinations were 
made in duplicate by the method generally followed and considered 
reliable. The fat in the milk was determined by the Adams gravi- 
metric method. The ash was determined b}^ combustion at a low tem- 
perature. The carbolrydrates were estimated by subtracting the sum 
of the protein, ether extract, water, and ash from 100. 

The determination of the ether extract in the feces necessarily 
involves an error, owing to the metabolic products present. Another 
source of error is in the protein determination. While the determi- 
nation of the total nitrogen is satisfactoiy, the factor for converting 
this nitrogen into protein is not perfectly reliable, and in many cases 
is very unsatisfactory. It is well known that not all of the nitrogen 
of a food is in the form of proteid compounds. In the case of the 
food materials used in these experiments, namely, bread and milk, 
over 97 per cent of the total nitrogen is in the form of proteids, and 
the error from nonproteid nitrogen in the food is therefore small. In 
the case of the feces, however, the kinds, proportions, and composi- 
tion of the nitrogenous ingredients are not well understood, and the 
estimate of " protein" is at best very crude. The errors involved in 
the determination of carbohydrates, by difference, are too well known 
to require discussion. Notwithstanding these imperfections of analyt- 
ical methods, which are not peculiar to these investigations but are 
common to all similar experiments, the results obtained in determining 
moisture, ash, total nitrogen, and heat of combustion are believed to 
be reasonably accurate, and the deductions drawn from them are 
regarded as reliable. 

The calorific value or heat of combustion of the various samples of 
food, feces, and urine was determined in the usual way by means of 
the bomb calorimeter. In the case of the milk and urine, weighed . 
blocks of cellulose were employed to absorb the liquid. The absorp- 
tion block was saturated, carefully dried, weighed, and again satu- 
rated with a weighed quantity of material. After drying at a tem- 
perature of 65° C. the block was burned in the calorimeter in the 



10 

usual way, a correction being made in the results for the heat of com- 
bustion of the block employed. 

DESCRIPTION OF SAMPLES OF FOOD MATERIALS. 

In the milling of the hard spring wheat great care was taken to 
secure representative samples. As in the former work, the milling 
was carried on under the supervision of Mr. C. E. Foster, of Minne- 
apolis, in one of the large flouring mills of that city. Two hundred 
pounds each of the three different kinds of flour were obtained from 
the mill. As soon as the samples were received at the laboratory 
smaller samples were drawn for analysis. 

For the experiments with soft winter wheat difficulty was experi- 
enced in securing samples of soft-wheat flours that were comparable 
with the grades of flour used in former work with hard spring wheat. 
The samples of hard wheat used in 1899-1901 were exhaustively 
milled and very little flour was left in the bran and middlings. 

The samples of soft wheat used in 1901-2 were, as is the custom with 
such wheats, less exhaustively milled and more flour was left in the 
offals. For this work sets of samples were obtained from two differ- 
ent milling companies, and in each case the different grades of flour 
were from a single lot of wheat. 

A description of the different sorts of wheat used in the experiments, 
and of the different grades of flour and milling products made from 
them, is here given. These are the samples the analyses of which are 
reported in Table 1. 

In addition to the various milling products mentioned, which are 
standard grades, other grades may be obtained by subdividing a grade 
or by mixing or blending two or more grades. Many of the flours 
which are placed upon the market are mixtures of two or more stand- 
ard grades of flour. 

No. 153. Hard Scotch Fife spring wheat, weighing 60 pounds per bushel; screened 
but not scoured. This wheat is representative of the hard spring wheat grown in the 
Northwestern wheat regions of the United States. 

No. 154. Entire-wheat flour from hard spring wheat No. 153. This is the product 
obtained by removing a portion of the bran and grinding the remainder of the grain. 
It includes the germ and other parts of the offal products which are excluded from 
the patent grades of flour. This flour is coarser in texture and darker in color than 
the patent and clear grades. The presence of fine bran particles prevents perfect 
granulation. Such "entire-wheat" flour is sometimes called "pulverized graham" 
or "natural flour." 

No. 155. Graham flour from hard spring wheat No. 153. This consists of the 
entire wheat kernel including bran, germ, and offal, ground into meal. Graham flour 
is practically wheat meal; no sieves or bolting cloths are employed in its manufacture, 
and coarse particles of bran, etc., may be observed in the flour. 

No. 156. Straight patent flour from hard spring wheat Nc. 153. This includes the 
first and second patent grades and the first clear or bakers' grade of flour described 
below. Ordinarily about 72 per cent of the screened wheat is recovered as straight 
patent flour. 



11 

No. 157. First patent flour from hard spring wheat No. 153. This is the highest 
grade of patent flour manufactured. Ordinarily about 56 per cent of the screened 
wheat is recovered as first patent flour, provided no straight flour is made. All of 
the patent grades of flour include the middlings which, by the former processes of 
milling, were not reduced to flour but were included in the offal products. The 
presence of the granular middlings gives a relatively high protein content to the 
patent grades of flour. 

No. 158. Second patent flour from hard spring wheat No. 153. This is similar to first 
patent, but. the bread made from it is a little darker in color and the gluten does not 
possess quite so high a power of expansion. The division of the flour into first, second, 
and straight patent grades is based entirely upon mechanical processes. In the higher 
grades of patent flour the gluten is distinctly different from that in the lower grades. 
The higher the grade of flour, the greater the power of expansion. It is this quality 
which enables the flour to absorb a large amount of water and as a result produce a 
large- sized loaf, and one of good physical properties. 

No. 159. First clear flour from hard spring wheat No. 153. After the first and second 
grades of patent flour are removed in milling about 12 per cent of first clear grade 
is obtained. This grade has a high protein content, but the gluten is different in 
character from that of the first and second patent grades of flour. As already 
explained, when the first and second patent grades and the first clear grade are 
blended as one product, the blend is called straight or standard patent flour. 

No. 160. Second clear or low-grade flour from hard spring wheat No. 153. After the 
removal of the first and second patent flours and the first clear flour about 5 per cent 
of the original wheat can be obtained as second clear or low-grade flour. This flour 
is much darker in color than the patent and first clear flours. It contains gluten, 
with a low power of expansion, and therefore is not so valuable for bread making as 
the higher grades of flour. Second clear flour is characterized by a high protein 
content, but for bread making this protein possesses poor physical properties. 

No. 161. Red-dog flour from hard spring wheat. This is the lowest grade of flour 
manufactured. It is sometimes used for feeding animals, and occasionally for human 
food. It is obtained largely from the parts adjacent to the germ or embryo, and is 
characterized by a high protein content, this protein, however, having different 
properties from that in the higher grades of flour. It possesses but little power of 
expansion, and the bread made from this grade of flour is dark in color and poor in 
quality, at least as regards its physical properties. In the process of milling the 
wheat germ is not included in the higher grades of flour, because its protein is not 
composed of gliadin and glutenin. Furthermore, the germ ferments readily, and 
thus when present in flour has a tendency to render it unsound. Ordinarily from 5 
to 8 per cent of the screened wheat is excluded as germ. This is utilized for the 
preparation of breakfast foods, for blending with other cereal food products, and for 
other purposes. Frequently, however, the wheat germ finds its way into the shorts 
and is used for cattle feed. 

No. 162. Wheat shorts or middlings from hard spring wheat No. 153. About 11.5 
to 12 per cent of the cleaned wheat is recovered as shorts, which consist of the fine 
bran that has been more or less completely pulverized. When the wheat germ is 
recovered with the shorts, the product is known as middlings. Such "middlings" 
must not be confused with the middlings obtained when wheat is milled by the old 
process. As previously stated, the material termed middlings in the old process is 
now reduced and recovered in the various grades of patent flour. 

No. 163. Bran from hard spring wheat No. 153. This consists of the coarsely ground 
episperm or outer covering of the wheat kernel. Ordinarily from 13 to 15 per cent 
of the cleaned wheat is recovered as bran. 



12 

No. 164. Entire-wheat bread. This was made of the flour from which sample No. 
154 was taken. 

No. 182. Graham bread. Thig was made of the flour from which sample No. 155 
was taken. 

Nos. 199 and 217. Straight patent flour bread. In making this bread flour was 
used from which sample No. 156 was taken. 

Nos. 165, 181, 198, and 216. Milk. Mixed milk, used in the digestion experiments. 

No. 218. Cleaned soft winter wheat, from Goshen, Ind., prepared for milling, of 
good quality, and weighing 60 pounds per bushel. The sample analyzed was ground 
in the laboratory in a Maercker mill. 

No. 221. Mixed-grade flour, ground from soft winter wheat No. 218, and consisting 
largely of straight flour with some lower grades and a little germ. As already 
explained, with exhaustive milling about 72 per cent of the screened wheat is recov- 
ered as straight flour, the grade most extensively used for bread making. If a lower 
percentage of wheat is recovered as flour, the sample is ranked, commercially, as a 
higher grade of patent flour because of its lighter color and other characteristic phys- 
ical properties. This sample, No. 221, was not strictly a straight grade flour, but 
was more properly a blend. 

No. 222. Entire-wheat flour, ground from soft winter wheat No. 218, after remov- 
ing a small amount of bran. This sample was different from the entire wheat used 
in former work with hard wheat; it had more of the characteristics of graham. It 
was, however, more finely pulverized than the graham flours used in the experi- 
ments made in 1899-1901. 

No. 267. Middlings obtained in the milling of the straight-grade flour No. 221, 
from soft winter wheat No. 218. Middlings include the fine particles of bran and 
germ, and, in case the wheat is not exhaustively milled, a small amount of the low- 
est grades of flour. 

No. 268. Bran, from soft winter wheat No. 218. 

No. 237. Soft winter wheat, of good quality, from North Lansing, Mich., weighing 
59 pounds per bushel, cleaned and prepared for milling. 

No. 240. Straight grade or standard patent flour, milled from soft wheat No. 237. 
From the analysis of the flour and the appearance of the offals, it would seem that 
this flour contained somewhat less than 72 per cent of the original wheat. It should 
be classed as a high grade rather than as a straight-grade flour. It possessed good 
bread-making qualities, but required more thorough mixing and kneading than 
hard-wheat flours. 

No. 238. Middlings, from soft winter wheat No. 237, obtained in milling flour No. 240. 

No. 239. Bran, from soft winter wheat No. 237, obtained in milling flour No. 240. 

No. 241. Entire- wheat flour, prepared from soft winter wheat No. 237. 

No. 242. Graham flour, obtained from soft winter wheat No. 237. 

No. 223. Mixed-grade flour bread. This was made of the flour from which sample 
No. 221 was taken. 

No. 231. Entire-wheat flour bread. This was made of the flour from which sample 
No. 219 was taken. 

No. 244. Straight patent flour bread. In making this bread flour was used from 
which sample No. 240 was taken. 

No. 251. Entire- wheat flour bread. This bread was made of the flour from which 
sample No. 241 was taken. 

No. 260. Graham-flour bread. The graham flour used was the lot from which 
sample No. 242 was taken. 

COMPOSITION OF SAMPLES OF FOOD MATERIALS. 

In Table 1, which follows, are given the results of the analyses of 
the wheat samples, of the flours and other products made from the 



13 



wheat, of the bread made from the flours, and of the milk consumed 
in the digestion experiments. 

Table 1. — Composition of wheats, flours, and offals, and of bread, and milk used in diges- 
tion experiments with hard and soft wheat breads. 



Samp It 
No. 



Whence obtained. 



Water. 



Protein, a 



Fat. 



Carbo- 
hydrates. 



Ash. 



Heat of 
combus- 
tion per 
gram, 
deter- 
mined. 



153 
154 
155 
156 
157 
158 
159 
160 
161 
162 
163 

164 
182 
199 
217 

218 
219 
221 
237 
238 
239 
240 
241 
242 
267 



223 
231 
244 
251 
260 
165 
181 
198 
216 
224 
232 
243 
258 
259 



Hard wheat: 

Wheat 

Entire-wheat flour 

Graham flour 

Straight patent flour 

First patent flour 

Second patent flour 

First clear flour 

Second clear flour 

Red dog flour 

Middlings 

Bran 

Bread made from — 

Entire- wheat flour 

Graham flour 

Straight patent flour 

Do 

Soft wheat: 

Wheat from Indiana 

Entire- wheat flour 

Mixed grade flour 

Wheat from Michigan 

Middlings 

Bran 

Straight patent flour 

Entire-wheat flour 

Graham flour 

Middlings 

Bran 

Bread made from — 

Mixed grade flour 

Entire-wheat flour 

Straight patent flour 

En tire- wheat flour 

Graham flour 

Milk, composite sample 

do 



.do 
.do 
.do 
.do 
.do 
.do 
.do 



Per cent. 
10.41 
13.51 
13.21 
12.38 
12.16 
12. 09 
11.92 
10.40 
10.26 
10.17 
11.47 

40.97 
42.68 
38.77 
37.37 

8.09 

9.60 

10.30 

10.25 

7.86 

8.74 

10.97 

11.01 

11.23 

9.76 

10.94 

39.56 
39. 50 
36.87 
37.62 
38.12 
87.81 
87.27 
87. 59 
87.14 
87.00 
86.56 
87.34 
87.67 
86. 50 



Per cent. 
15.50 
13.72 
14.21 
13.60 
13.31 
13.05 
17.73 
20. 00 
21.83 
18.64 
17.10 

9.32 
9.54 
9.63 
9.74 

13.16 
12.80 
12.30 
12.34 
17.91 
14.96 
10.92 
12.01 
12.24 
18.34 
16.72 

8.01 
8.53 
7.59 



3.25 
3.13 
3.04 
3.38 
3.31 
3.32 
2.99 
3.00 
3.25 



Per cent. 
2.28 
1.69 
2.01 
1.30 
1.21 
1.37 
1.98 
3.17 
6.10 
6.04 
4.23 

.19 
.29 
.04 
.26 

1.52 
1.54 

.93 
1.35 
5.18 
4.41 

.50 
1.53 
1.41 
4.65 
4.42 

.60 
1.02 

.38 
1.08 

.87 
3.80 
4.00 
3.82 
4.15 
4.38 
4.67 
4.09 
3.85 
4.45 



Per cent. 
69.88 
70.10 
68.56 
72.04 
72.93 
73.03 
67.37 
64.24 
57.72 
59.72 
59.89 

48.75 
46.10 
51.06 
52.12 

75.38 
74.40 
75.94 
74.23 
65.09 
65.78 
77.15 
74.17 
73.27 
64.05 
61.20 

51.32 

49.49 

54.67 

51.70 

51.20 

4.34 

4.71 

4.81 

4.57 

4.52 

4.68 

4.81 

4.75 

5.03 



Per cent. 
1.93 



1.00 
2.19 
4.09 
5.43 
7.31 

.77 

1.39 

.50 

.51 

1.85 
1.66 

.53 
1.83 
3.96 
6.11 

.46 
1.28 
1.85 
3.20 
6.72 



Calories. 
4.023 
3.877 
3.971 
3.861 
3.960 
3.904 
4.072 
4.112 
4.430 
4.314 
4.187 

2.535 

2.495 
2.594 
2.647 

4.090 
4.020 
4.010 
4.000 
4.256 
4.108 
3.799 
3.860 
3.906 



2.710 

2.640 

2. 610 

2.690 

2.620 

.700 

.746 

.729 

.744 

.780 

.813 

.742 

.735 

.777 



a In all samples except milk, protein is Nx5. 70; in milk it is Nx6. 25. 

The hard Scotch Fife spring wheat selected for the experiments 
(sample No. 153) was characterized by a very high protein content, 
namely, 15.5 per cent. In an earlier publication of this Department 
showing the average composition of a large number of American feed- 
ing stuffs" the protein content of wheat is given as 11.9 per cent. The 
highest percentage of protein there recorded is 17.2 per cent and the 
lowest 8.1 per cent. It will be observed that the wheat from which 
these flour samples were obtained contained nearly this maximum 
amount of proteid material. In the investigations with hard wheat 
previously reported, 6 the wheat employed contained 12.65 per cent 
protein. The average amount of protein in the same variety of wheat 

«U. S. Dept. Agr., Office of Experiment Stations Bui. No. 11, p. 17. 
&U. S. Dept. Agr., Office of Experiment Stations Bui. No. 101. 



14 

is found to vary materially from year to year, depending among other 
things upon the amount of rainfall and the climatic conditions under 
which the wheat has matured. The wheat crop produced in the north- 
western United States in 1900 was unusually rich in protein. The 
rainfall and climatic conditions seemed to be particular^ favorable for 
producing wheat and other grains with a high nitrogen content. While 
the wheat employed in this investigation contained somewhat more 
protein than is found in average wheat, in the author's opinion the 
percentage is no greater than in average wheat grown in the north- 
western United States in 1900. All of the flour samples from this 
wheat were relatively richer in protein than those in similar investi- 
gations with hard wheat in 1898-99, owing to the high nitrogen con- 
tent of the wheat. The differences in the protein content of the several 
grades of flour ground from the wheat were comparatively small. 

There was a higher percentage of fat in the middlings than in the 
bran, owing to the presence of the germ in the former. Red-dog flour 
is the richest, as regards both fat and protein, of the products ground 
from the wheat. In the case of the patent and clear grades of -flour, 
the heat of combustion as determined was found to agree closely with 
the heat of combustion obtained by calculation, using the usual factors, 
namely, 9.3 calories per gram a for fat, 5.9 for protein, and 4.2 for 
carbohydrates. As pointed out in a previous report, 6 the percentage 
of ash in the various products of wheat was lowest in the first 
patent flour and highest in the red-dog flour. Each grade of flour, 
beginning with the first patent, was found to contain proportionally 
more ash than the preceding grade. In fact, as noted previously, the 
grade of flour can be determined from the amount of ash present. In 
the analyses reported above the ash content is greater than in the 
samples employed in the earlier work with hard wheat in this labora- 
tory. There appears to be a close relationship between the amounts 
of ash and protein present in flour and other milled products of wheat, 
an} 1 material increase in protein being accompanied by a correspond- 
ing increase in mineral matter. This has often been attributed to the 
phosphorus associated with the proteids. Late work of Osborne c 
indicates that the total amount of phosphorus in wheat proteids is 
too small to account for the increase in mineral matter just alluded to. 

The distribution of the nitrogen and ash constituents of the wheat 
berr}^ has been frequently studied, and it is interesting to note some 
comparatively recent American work on the subject, particularly as 
the investigations were made with wheats grown in the United States, 
which are therefore directly comparable with the wheats used in the 
investigation reported in this bulletin. 

Mrs. Ellen H. Richards and Miss Lottie A. Bragg d studied the distri- 

a~U. S. Dept. Agr., Office of Experiment Stations Bui. 101, p. 12. & lb., p. 9. 

c Connecticut State Station Rpt. 1900, p. 464. <* Tech. Quart., 3 (1890) , p. 246, 



15 

bution of nitrogen and phosphorus in winter and spring wheat and 
their milling products, in both cases the milling products having been 
ground from the same lots of wheat. The results obtained are shown 
in the following table, which includes also values for protein obtained 
by multiplying the figures for nitrogen by 6.25: 

Table 2. — Nitrogen and phosphorus in wheat and its milling products. 



Milling products. 



St. Louis winter wheat: 

Whole wheat 

Royal patent flour . . 

Extra fancy flour . . . 

Low-grade flour 

Middlings 

Bran 

Minnesota spring wheat 

Whole wheat ....... 

Patent flour 

Bakers' flour 

Shorts 

Bran 



Water. 


Phos- 
phorus. 


Nitrogen. 


Per cent. 


Per cent. 


Per cent. 


12.85 


0.262 


1.87 


13.37 


.051 


1.39 


12.51 


.100 


1.78 


11.94 


.100 


2.08 


11.21 


.225 


2.73 


12.15 


.828 


2.62 


11.09 


.230 


2. 24 


12.29 


.050 


2.10 


12.14 


.091 


2.40 


11.27 


.560 


2.78 


11.23 


.830 


2. 55 



Protein 
(NX 6.25). 



Per cent. 
11.7 
8.7 
11.1 
13.0 
17.1 
16.4 

14.0 
13.1 
15.0 
17.4 
15.9 



The figures in the table indicate that, while a larger part of the protein 
is recovered in the flour than is the case with the phosphorus, there is, 
nevertheless, a parallelism in the proportion of protein and phosphorus 
in the different milling products. 

At the Arkansas Experiment Station, Teller a made a very thorough 
and detailed stud}^ of the ash constituents of a sample of locally grown 
medium hard winter wheat and its milling products. In milling 3,000 
pounds of uncleaned wheat, 1.83 per cent was recovered as screenings 
and 0.33 per cent as tailings, the percentage of milling products being 
as follows: Patent flour 25.80, straight flour 42, low-grade flour 3.87, 
dust room contents 1.17, ship stuff 1.13, and bran 23.80. The loss of 
material in grinding — that is, the material unaccounted for — was 
therefore only 0.07 per cent. 

The principal ash constituents and the sulphur and nitrogen in the 
whole wheat and the different milling products were as follows: 

Table 3. — Ash constituents and nitrogen of winter wheat and its milling products. 



Milling products. 



Total 
ash.b 



In total ash. 



Silica. 



Ferric 
oxid. 



Potash. 



Lime. 



Mag- 
nesia. 



Phos- 
phoric 
acid. 



Sul- 
phur. 



Nitro- 
gen. 



Wheat 

Patent flour 

Straight flour 

Low-grade flour 

Dust room material 

Ship stuff 

Bran 



Per ct. 

1.62 

.31 

.40 

.70 

2.50 

3.08 

5.25 



Per ct. 

1.04 

2.33 

1.28 

.50 

1.34 

.49 

.97 



Per ct. 
0.27 
.47 
.26 
.25 
.30 
.37 
.27 



Per ct. 
29.70 
38.50 
36.31 
32.27 
30.85 
28.03 
28.19 



er ct. 
3.10 
5.59 
5.65 
4.51 
3.53 
2.80 
2.50 



Per ct. 

13.23 

4.39 

6.44 

9.33 

12.90 

13.27 

14.76 



Per ct. 
52.14 
48.05 
49.32 
53.10 
49.94 
54. 62 
52.81 



Per ct. 
0.13 
.09 
.10 
.16 
.15 
.17 
.21 



Per ct. 
1.96 
1.54 
1.75 
2.13 
2.17 
2.78 
2.73 



a Arkansas Station Bui. 42, pts. 1, 2. 

& This sum includes values which are given for alumina, chlorin, zinc, and sulphur trioxid, which 
are not quoted in the table. The author regards the values for sulphur present in the different 
materials as more reliable than those for sulphvu trioxid in the ash, owing to a probable volatilization 
of sulphur in burning to obtain the ash. The other constituents omitted are not of much importance, 
the alumina and zinc being accidentally present. 



16 

Teller points out that about 87.5 per cent of the entire phosphoric 
acid, 78.5 per cent of the potash, and 37.5 per cent of the nitrogen 
present in the wheat berry are recovered in the milling products 
ordinarily used as cattle feeds. As will be seen from the above table, 
the percentage of phosphoric acid increases as the grade of flour 
decreases, being least in the patent flour and greatest in low-grade 
flour, the proportion present in the latter being greater than in any of 
the milling products except ship stuff; in other words, as shown by these 
figures, the phosphoric acid content, generally speaking, increases in 
passing from the center of the wheat berry to the outer layer, the 
inner portion yielding the fine flour and the outer portion the bran. 
The table also shows that in the various milling products the propor- 
tion of nitrogen (and hence that of protein, since the latter is computed 
by multipl} T ing nitrogen by a constant factor) varies in practically the 
same wa}^ as the phosphorus. 

The parallelism between protein and phosphorus, which was spoken 
of above, is borne out by the analytical data quoted, though it does 
not necessarily follow that the phosphorus present occurs in the true 
proteids. 

As a whole, it has been the aim in the experiments conducted at the 
University of Minnesota to include standard types and varieties of 
hard and soft wheat flours, milled under different conditions. The 
differences in the percentages of flour recovered from the wheat used 
necessarily make slight differences in the composition and character- 
istics of the grades of flour obtained. The soft wheat products were 
of different character from the samples of similar products from hard 
wheat. The hard wheats had been exhaustively milled, as is the 
usual custom, in one of the large mills of Minneapolis, while the soft 
winter wheats were ground by mills of smaller capacity using some- 
what different milling systems, and, as is the general commercial prac- 
tice, were less exhaustively milled. 

In general, the flours from soft wheat were somewhat similar to, 
though not in every respect like those from, hard wheat, because of 
the differences in the kinds of wheat used and percentages of flour 
recovered. The graham flour contained the largest percentage of pro- 
tein, fat, and ash, while the patent grades of flour contained the small- 
est amounts of these ingredients. A noticeable difference in the 
mechanical composition of the three grades of soft wheat flour was 
observed. With the process of milling followed, some granular mid- 
dlings were left in the offals which would have been recovered in the 
straight and other grades of flour with more exhaustive milling. This 
results in a straight-grade flour containing slightly less protein than 
the product of exhaustive milling, as the granular middlings are rich 
in this nutrient. The particles or granules of the graham flour were 



17 

much larger than those of either the entire-wheat or the straight-grade 
flour. The comparative sizes of granules from graham, entire-wheat, 
and straight-grade flours ground from soft wheat are shown in the 
micro-photographs reproduced in Plate I, figs. 1 and 2, and Plate II, 
fig. 1, p. 48. 

COMPOSITION OF FECES AND URINE OBTAINED IN DIGESTION 

EXPERIMENTS. 

The composition of the dry matter of the feces from the digestion 
experiments is given in Table 4, while Table 5 records the amount, 
specific gravit}^, and percentage of nitrogen of the urine. 

A description of the samples of feces and urine follows: 

Nos. 178, 199, 180, 195, 196, 197, 213, 214, and 215 represent the feces which were 
obtained in the digestion experiments with hard spring wheat products. 

Nos. 225, 226, 227, 233, 234, 235, 245, 246, 247, 252, 253, 254, 261, 262, and 263, the 
feces which were obtained in the digestion experiments of 1901-2 with soft winter 
wheat. 

Nos. 166-177, 183-194, and 200-212, the urine from the digestion experiments with 
hard spring wheat products. 

Nos. 228, 229, 230, 236, 237, 238, 248, 249, 250, 255, 256, 257, 264, 265, and 266, the 
urine obtained in the experiments with soft winter wheat. 

Table 4. — Composition of dry matter of feces from digestion experiments with hard and 

soft wheat breads. 



Sample 

No. 



178 
179 
180 
195 
196 
197 
213 
214 
215 

225 
226 

227 
233 
234 
235 
245 
246 
247 
252 
253 
254 
261 
262 
263 



Whence obtained. 



Experiments with hard wheat 

Experiment No. 242 

Experiment No. 243 

Experiment No. 244 

Experiment No. 245 

Experiment No. 246 

Experiment No. 247 

Experiment No. 248 

Experiment No. 249 

Experiment No. 250 

Experiments with soft wheat: 

Experiment No. 309 

Experiment No. 310 

Experiment Fo. 311 

Experiment No. 312 

Experiment No. 313 

Experiment No. 314 

Experiment No. 315 

Experiment No. 316 

Experiment No. 317 

Experiment No. 318 

Experiment No. 319 

Experiment No. 320 

Experiment No. 321 ! 

Experiment No. 322 

Experiment No. 323 



Protein 

(Nx 6.25) 



Per cent. 
30.25 
28.37 
25.00 
23.25 
23.31 
21.67 
29.94 
28. 56 
23.94 

14.10 
21. 83 
26. 75 
14.31 
16.76 
20.06 
22.61 
23.13 
25.34 
17.94 
21.00 
18.67 
19.50 
17.86 
19.13 



Fat. 



Per cent. 
12.26 
7.45 
7.44 
8.70 
5.61 
6.41 
17.46 
11.44 
9.30 

17.04 

15.84 
9.10 
5.36 

10.32 
4.32 
8.58 

13.13 

15.26 
5.31 

11.65 
6.00 
6.44 

13.98 
8.25 



Carbo- 
hydrates. 



Per cent. 
34.42 
35.37 
41.35 
50.16 
47.59 
50.48 
25. 02 
26.42 
36.47 

45. 15 
38.92 
39.40 
60.48 
55.98 
56.51 
43.99 
38.92 
32.59 
56.28 
46.38 
51.76 
57.06 
51.14 
52.68 



Ash. 



Per cent. 
23.07 
28.81 
26.21 
17.89 
23.49 
21.44 
27. 58 
33.58 
30.29 

23.71 
23.41 
24.75 
19.85 
16.94 
19.11 
24.82 
24.82 
26.81 
20.47 
20.97 
23.57 
17.00 
17.02 
19.94 



Heat of 
combus- 
tion per 
gram 
deter- 
mined. 



Calories. 
4. 63S 
4.070 
4.351 
4.415 
3.960 
4.170 
4. 720 
4. 265 
4.654 

5.030 
5.300 
4.400 
4.340 
4. 420 
4.160 
5.050 
5.160 
5.360 
4.290 
4.410 
3.990 
4.220 
4.470 
4.170 



19047— No. 126—03- 



18 

Table 5. — Amount, specific gravity, and nitrogen of urine from digestion experiments with 

hard and soft wheat breads. 



Sample 


Subject 


No. 


No. 


166 


1 


169 


1 


172 


1 


175 


1 


167 


2 


170 


2 


173 


2 


176 


2 


168 


3 


171 


3 


174 


3 


177 


3 


183 


1 


186 


1 


189 


1 


192 


1 


184 


2 


187 


2 


190 


2 


193 


2 


185 


3 


188 


3 


191 


3 


194 


3 


200 


1 


204 


1 


207 


1 


210 


1 


201 


2 


205 


2 


208 


2 


211 


2 


203 


3 


206 


3 


209 


3 


212 


3 


228 


1 


229 


2 


230 


o 


236 


1 


237 


2 


238 


3 


248 


1 


249 


2 


250 


3 


255 


1 


256 


2 


257 


3 


264 


1 


265 


2 


266 


3 



Whence obtained. 



Experiments with hard wheat 
Experiment No. 242 — 

First day 

Second day 

Third day*. 

Fourth day 

Experiment No. 243— . 

First day 

Second day 

Third day 

Fourth day 

Experiment No. 244— 

First day 

Second day 

Third day 

Fourth day 

Experiment No. 245 — 

First day 

Second dav 

Third day 

Fourth day 

Experiment No. 246 — 

First day 

Second day. ■. 

Third day 

Fourth day 

Experiment No. 247 — 

First day 

Second day 

Third day 

- Fourth day 

Experiment No. 248 — 

First day 

Second day 

Third day* 

Fourth day 

Experiment No. 249 — 

First day 

Second day 

Third day 

Fourth day 

Experiment No. 250— 

First day 

Second day 

Third day 

Fourth day 

Experiments with soft wheat: 

Experiment No. 309 

Experiment No. 310 

Experiment No. 311 

Experiment No. 312 

Experiment No. 313 

Experiment No. 314 

Experiment No. 315 

Experiment No. 316 

Experiment No. 317 

Experiment No. 318 

Experiment No. 319 

Experiment No. 320 

Experiment No. 321 

Experiment No. 322 

Experiment No. 323 



Total 
amount 
voided. 



Grams. 
1, 368. 
1, 350. 
1,463.5 
1,326.0 

1,805.0 
2, 112. 
2, 298. 
2, 248. 

1,991.0 

1, 720. 
1,679.0 
1, 947. 

1,270.0 
1,210.0 
1,212.0 
1,102.0 

1,943.0 
1,732.0 

2, 188. 

2, 368. 

1,851.0 
1,581.0 
1, 614. 5 
1,338.0 

1, 124. 
1,077.0 
1,068.0 
1,110.0 

1,943.0 
1,698.0 
2,182.0 I 
2,023.U ! 

1. 123. 
1, 242. 
1,601.0 
2,463.0 

6. 023. 1 
4, 296. 2 

4. 486. 2 
5, 652. 9 
5, 201. 7 
4,115.6 
7,317.4 
6, 556. 6 
1, 747. 6 
7, 889. 1 
6, 910. 1 
5, 476. 6 
5,210.1 
4, 532. 
4, 508. 8 



Specific 
gravity. 



1.026 
1.023 
1.027 
1.029 

1.016 
1.015 
1.015 
1.017 

1.020 
1.021 
1.025 
1.028 

1.030 
1.030 
1.030 
1.028 

1.015 
1.015 
1.015 
1.014 

1.024 
1. 025 
1.027 
1.027 

1.027 
1.031 
1.030 
1.029 

1.014 
1.015 
1.015 
1.014 

1.028 
1.026 
1.022 
.1.016 

1.016 
1.020 
1.019 
1.019 
1.020 
1. 022 
1.016 
1.019 
1.020 
1.016 
1. 020 
1.021 
1.020 
1.020 
1.022 



Nitrogen. 



Per cent. 
1.58 
1.45 
1.65 
1.74 



EXPERIMENTAL METHODS. 



The methods followed in all of the experiments here reported are 
practically identical with those described in detail in the previous 
publication a already referred to, and need onty be briefly outlined. 

The bread from the different sorts of flour was eaten with milk; the 
amount of either was not limited, but the quantities eaten at each meal 
were recorded. The separations of the feces were made by means of 

«U. S. Dept. Agr., Office of Experiment Stations Bui. 101. 



19 

charcoal taken with a meal of bread and milk, which gives feces of a 
characteristic color and consistency. The digestibility of the nutrients 
of the diet as a whole was taken as the difference between the amounts 
in the food and those in the feces, no attempt being made to determine 
the metabolic products of the feces/* 

In order to compute the digestibility of the nutrients of the bread 
alone, it was assumed that 97 per cent of the protein, 95 per cent of 
the fat, and 98 per cent of the carbohydrates of milk were digested. 
The undigested nutrients of the milk as calculated by the use of these 
factors subtracted from the nutrients of the total feces give the esti- 
mated undigested nutrients from bread, which, subtracted from the 
total nutrients of the bread, give the digestible nutrients in bread. 
The latter, divided by the total nutrients in the bread, give the coeffi- 
cients of digestibility of bread alone. 

The values used for the digestibility of the nutrients of milk have 
been deduced from the results of a large number of digestion experi- 
ments with milk. Even if, in the experiments here reported, the diges- 
tibility of the milk nutrients varied from these assumed coefficients, 
the figures for the digestibility of the nutrients of the different kinds 
of bread are still strictly comparable because the same factors for 
milk were used in all cases. 

As has been already explained, b the energy of the estimated feces 
from bread alone was computed by proportion from the energy of the 
total feces. The ratio of the heat of combustion of the bread feces 
as computed by factors to the actual energy was assumed to be the 
same as the ratio of the computed energy of total feces to the heat of 
combustion as determined. 

Although the energy of the urine was determined, in the calculation 
of the availability of the energy of the total food and of the bread 
alone, it was assumed, for the sake of uniformity with experiments 
previously reported, that 1.25 calories of energy would appear in the 
urine for every gram of digestible protein in the total food or in the 
bread alone. For the sake of making an approximate estimate of the 
available energy in those experiments where the digestibility of the 
bread fat could not be computed, it was assumed that 90 per cent of 

«It should be observed that the results thus obtained do not represent actual 
digestibility. The true digestibility could be found by subtracting from the ingredi- 
ents of the food the corresponding ingredients of the feces that come only from undi- 
gested portions of the food. But no satisfactory method has been found for separating 
these from the metabolic products in the feces, which consist largely of the residues 
of the digestive juices that have not been reabsorbed. These latter represent the 
cost of digestion as expressed in terms of food ingredients. What the results of these 
experiments do represent, therefore, is the proportions of the food, or of the several 
ingredients, that are available to the body for purposes other than digestion itself. 
In accordance with common usage, however, the term digestibility, which indicates 
the apparent digestibility, has been employed here; the term availability is some- 
times used to express the same idea. 

&TJ. S. Dept. Agr., Office of Experiment Stations Bui. 101, p. 22. 



,20 

the fat of the bread was digestible. The results thus found would 
probably be below rather than above what was actually the case. 

As in the preceding experiments, the balance of income and outgo 
of nitrogen was learned by determining the daily amounts ingested 
in the food and excreted in the urine and feces. In the experi- 
ments with soft winter wheat in 1901-2 determinations were also made 
of the phosphoric acid in the samples of food, feces, and urine. Such 
data, however, are reserved for further study. 

The particular difference between the digestion experiments given 
here and those formerly reported is in the length of the experimental 
period, this being four days long here and only two in the earlier 
experiments. The longer experimental period is believed to be pref- 
erable, because it is generally considered that there is less danger 
of error due to uncontrollable factors that may vitiate the results in 
a short digestion period. 

As is well known, the results obtained from a digestion experiment 
are not absolute, but only relative. But inasmuch as in the diges- 
tion experiments reported in this bulletin the object is to deter- 
mine the relative rather than the absolute digestibilit}^ of three 
different kinds of bread, it is believed that the results obtained are 
satisfactory for this purpose, because whatever error may be intro- 
duced in one experiment is introduced alike in all of any given series, 
since the conditions were kept uniform throughout the series. While 
the results of a single digestion experiment are open to criticism, the 
results obtained from a series of experiments are much less so and are 
of value in determining whether one food is more digestible than 
another under similar experimental conditions. Hence in discussing 
the results obtained from these digestion experiments they are con- 
sidered in relation to one another rather than alone. 

DETAILS OF THE DIGESTION EXPERIMENTS WITH BREAD FROM 
DIFFERENT GRADES OF HARD SPRING WHEAT FLOUR. 

The details of the digestion experiments with hard wheat products 
are given in the following pages. Nine digestion experiments, each of 
four days' (or twelve meals') duration were made with three different 
subjects. In every case the diet consisted of bread and milk, and all of 
the experiments were conducted in the same manner, except that bread 
made from a different kind of flour was used in each series. In making 
the bread no shortening or milk was used, but simply yeast, flour, salt, 
and water. 

The subjects were university students who spent from three to four 
hours each day at light muscular work out of doors. All had served 
as subjects in former digestion experiments and were thoroughly 
familiar with the requirements of such work. 

The experiments were practically made in triplicate — that is, the 
same kind of an experiment was made with each of three subjects at 



21 

the same time. The order in which they were conducted was as follows: 
The first series of experiments (with entire-wheat bread) extended 
from April 17 to April 20, inclusive; the second series (with graham 
bread) from April 23 to April 26, inclusive; and the third series (with 
bread from standard patent flour) from May 1 to May 1, inclusive. 
The experiments were taken up in this order because of the difficulty 
experienced in previous experiments with a graham bread and milk 
diet. It was believed that the investigation could be conducted to 
better advantage by having the graham bread experiment between the 
others, rather than at the beginning or close of the series. The four 
days' diet of graham bread and milk caused a slight irritation of the 
digestive tract and a slight attack of gastritis with two of the subjects. 
The following tables, Nos. 6 to 14, and the accompanying data show 
the kind of food consumed, the subject experimented upon, the body 
weight at the beginning and at the close of the experiment, and the 
date and duration. Then follow statistics of the total nutrients in 
the food and the feces, and the heat of combustion of each, and after 
each of the tables statistics are given of the income and outgo of 
nitrogen during the experiment. 



DIGESTION EXPERIMENT NO. 242. 

Kind of food. — Milk, and bread made from entire-wheat flour. 

Subject. — University student No. 1, 22 years old, employed about 
four hours per day at manual labor. 

Weight. — At the beginning of the experiment, 168 pounds; at the 
close, 168 pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
April 17, 1901. 

Table 6. — Results of digestion experiment No. 24%- 



Sample 
No. 




Weight 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


164 


Food consumed: 

Bread 


Grams. 
3,550.0 
9, 950. 


Grams. 
330.9 
323.4 


Grams. 

6.7 

378.1 


Grams. 

1, 730. 7 

431.8 


Grams. 
27.3 
79.6 


Calories. 
8,998 
6,965 


165 


Milk ; 




Total 






654.3 


384.8 


2, 162. 5 


106.9 


15, 963 




Feces (water free) 






178 


214.0 


64.7 

9.7 


26.2 


73.7 
8.6 


49.4 


992 




Estimated feces from food other 
than bread 






Estimated feces from 
bread 














55.0 




65.1 








Total amount digested 














589.6 
275 9 


358 6 


2, 088. 8 
1, 665. 6 


57.5 


14,971 




Estimated digestible nutrients 
in bread ; 






Coefficients of digestibility oi 
total food 












Per cent 


Per cent. 
90.1 

83.4 


Per cent. 
93.2 


Per cent. 
96.6 

96.2 


Per cent. 
53.8 


Per cent. 
93.8 




Estimated coefficients of diges- 
tibility of bread 




« 93.0 




Proportion of energy actually 
available to body: 
In total food 








88.2 




In bread alone 












a 89.1 















a Estimated on the assumption that 90 per cent of the fat in the bread is digestible. 



22 

During this experiment the subject eliminated 5,508 grams urine, 
containing 88.42 grams nitrogen. The average nitrogen balance per 
day was therefore as follows: Income in food, 27.47 grams; outgo in 
urine, 22.10 grams and in feces, 2.59 grams, implying a gain of 2.78 
grams nitrogen, corresponding to 17.4 grams protein. 

DIGESTION EXPERIMENT NO. 243. 

Kind of food. — Milk, and bread made from entire- wheat flour. 

/Subject. — University student No. 2, 22 years old, employed about 
four hours per day at manual labor. 

Weight. — At the beginning of the experiment, 156 pounds; at the 
close, 155 pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
April 17, 1901. 

Table 7. — Results of digestion experiment No. 24S. 



Sample 

No. 




Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


164 


Food consumed: 


Grams. 
3, 101. 
12, 310. 


Grams. 
289.0 
400.1 


Grams. 

5.9 

467.8 


Grams. 

1,511.8 

534.3 


Grams. 
23.9 
98.5 


Calories. 
7,860 
8,617 


165 


Milk 




Total 










689.1 


473.7 


2, 046. 1 


122.4 


16. 477 




Feces ( water free ) 






179 


180.0 


51.1 

12.0 


13.4 


63.7 
10.7 


51.9 


733 




Estimated feces from food other 
than bread 






Estimated feces from 
bread 














39.1 




53.0 




















638.0 
249.9 


460.3 


1, 982. 4 
1,458.8 


70.5 


15,744 




Estimated digestible nutrients 
in bread 








Coefficients of digestibility of 
total food 












Per cent. 


Per cent. 
92.6 

86.5 


Per cent. 
97.2 


Per cent. 
96.9 

96.5 


Per cent. 
57.6 


Per cent. 
95.6 




Estimated coefficients of digest- 




a 90. 4 




Proportion of energy actually 
available to body: 
In total food 








90.7 
















a 90.0 



















a Estimated on the assumption that 90 per cent of the fat in the bread is digestible. 

During this experiment the subject eliminated 8,463 grams urine, 
containing 80.95 grams nitrogen. The average nitrogen balance per 
da} r was therefore as follows: Income in food, 28.68 grams; outgo in 
urine, 20.24 grams, and in feces, 2.09 grams, implying a gain of 6.35 
grams nitrogen, corresponding to 39.7 grams protein. 



23 

DIGESTION EXPERIMENT NO. 244. 

Kind of food. — Milk, and bread made from entire- wheat flour. 

Subject. — University student No. 3, 24 years old, employed about 
four hours per day at manual labor. 

Weight.- — At the beginning of the experiment, 161 pounds; at the 
close, 160 pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
April 17, 1901. 

Table 8. — Results of digestion experiment No. 244- 



Sample 

No. 




Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


164 


Food consumed: 


Grams. 

3, 760. 

14,843,0 


Grams. 
350.4 
482.4 


Grams. 

7.1 

564.0 


Grams. 

1, 833. 1 

644.2 


Grams. 

28.9 

118.8 


Calories. 
9,530 


165 


Milk 


10, 390 




Total 








832.8 


571.1 


2,477.3 


147.7 


19, 920 










180 


215.1 


53.8 
14.5 


16.0 


88.9 
12.9 


56.4 


936 




Estimated feces from food other 






Estimated feces from 














39.3 




76.0 








Total amount digested 
















779.0 
311.1 


555.1 


2, 388. 4 
1,757.1 


91.3 


18, 984 




Estimated digestible nutrients 
in bread 








Coefficients of digestibility of 
total food 












Per cent. 


Per cent. 
93.5 

88.8 


Per cent. 
97.2 


Per cent. 
96.4 

95.9 


Per cent. 
61.8 


Per cent. 
95.3 




Estimated coefficients of digest- 
ibility of bread 




(i94.3 




Proportion of energy actually 
available to body: 

In total food 








90.4 
















a 90. 2 










l 







a Estimated on the assumption that 90 per cent of the fat in the bread is digestible. 

During this experiment the subject eliminated 7,337 grams urine, 
containing 108.24 grams nitrogen. The average nitrogen balance per 
day was therefore as follows: Income in food, 34.66 grams; outgo in 
urine, 27.06 grams, and in feces, 2.15 grams, implying a gain of 5.45 
grams nitrogen, corresponding to 34.1 grams protein. 



DIGESTION EXPERIMENT NO. 245. 

Kind of food. — Milk, and bread made from graham flour. 

Subject.— University student No. 1. 

Weight. — At the beginning of the experiment, 168 pounds; at the 
close, 167 pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
April 23, 1901. 



24 



Table 9. — Results of digestion experiment No. 245. 



Sample 
No. 




Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


182 


Food consumed: 

Bread 


Gravis. 
3, 342. 
10, 207. 


Grams. 
318.8 
319.5 


Grams. 

9.7 

408.3 


Grams. 

1, 540. 7 

480. 8 


Grams. 
46.5 
90.8 


Calories 
8,337 


181 


Milk 


7,614 




Total 








638.3 


418.0 


2, 021. 5 


137.3 


15, 951 




Feces (water free) 






195 


300. 1 fi9. 8 


26.1 
20.4 


150.5 
9.6 


53.7 


1,325 




Estimated feces fromfood other 
than bread 




9.6 


302 












Estimated feces from 
bread 




60.2 


5.7 


140.9 




1,023 




Total amount digested 










568.5 

258.6 


391. 9 


1 . 871 . 


83.6 


14, 626 
7,314 




Estimated digestible nutrients 
in bread 




4.0 i 1.399.8 




Coefficients of digestibility of 
total food 




i 






Per cent. 


Per cent. 
89.1 

81.1 


Per cent. 
93.8 

41.2 


Per cent. 
92.6 

90.9 


Per cent. 
60.9 


Per cent. 
91 7 




Estimated coefficients of digest- 
ibility of bread 




87.7 




Proportion of energy actually 
available to body: 
In total food 






87.2 
















83.9 



















During this experiment the subject eliminated 4,794 grams urine, 
containing 87.79 grams nitrogen. The average nitrogen balance per 
day was therefore as follows: Income in food, 26.74 grams; outgo 
in urine, 21.95 grams, and in feces 3.79 grams, implying a gain of 1 
gram nitrogen, corresponding to 6.3 grams protein. 

DIGESTION EXPERIMENT NO. 246. 

Kind of food. — Milk, and bread made from graham flour. 

Subject. — University student No. 2. 

Weight. — At the beginning of the experiment, 154 pounds; at the 
close, 152.7 pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
April 23, 1901. 



Table 10. — Results of digestion experiment No. 24&- 



Sample 
No. 




Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


182 


Food consumed: 

Bread 


Grams. 
2, 855. 


Grams. 
272. 4 


Grams. 

8.3 

422.7 


Grams. 

1,316.2 

497.8 


Grams. 
39.7 
94.1 


Calories. 
7, 123 


181 


Milk 


10, 568. 330. 8 


7,883 




Total 












603. 2 


431.0 


1,814.0 


133.8 


15, 006 




Feces (water free) 






196 


259.0 


60.4 
9.9 


14.5 


123. 3 
10.0 


60.8 


1,026 




Estimated feces from food 






Estimated feces irom 














50.5 




113.3 
























542. 8 
221. 9 


416.5 


1,690.7 
1,202.9 


73.0 


13, 980 




Estimated digestible nutrients 
in bread 



















25 



Table 10. — Results of digestion experiment No. 246 — Continued. 



Sample 
No. 



Coefficients of digestibility of 

total food 

Estimated coefficients of diges- 
tibility of bread 

Proportion of energy actually 
available to body: 

In total food 

In bread alone 



Weight 

of 
material, 



Per cent. 



Protein. 



Fat. 



| Carbo- 
I hydrates. 



Per cent. \ Per cent. 
90.0 96.6 



81.5 



Per cent. 
93.2 



91.4 



Ash. 



Per cent. 
54.6 



Heat of 
combus- 
tion. 



Per cent. 
93.2 



a 88. 9 



88.6 
a 85.1 



a Estimated on the assumption that 90 per cent of the fat in the bread is digestible. 

During this experiment the subject eliminated 8,231 grams urine, 
containing 81.73 grams nitrogen. The average nitrogen balance per 
day was, therefore, as follows: Income in food, 25.16 grams; outgo 
in urine, 20.43 grams, and in feces, 2.91 grams, implying a gain of 1.79 
grams nitrogen, corresponding to 11.2 grams protein. 

DIGESTION EXPERIMENT NO. 247. 

Kind of food. — Milk, and bread made from graham flour. 

Subject. — Universit}^ student No. 3. 

Weight. — At the beginning of the experiment, 161 pounds; at the 
close, 157 pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
April 23, 1901. 

Table 11. — Results of digestion experiment No. 247. 



Sample 
No. 




Weight 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 

com- 
bustion. 


182 


Food consumed: 


Grams. 
3, 440. 
12, 475. 


Grams. 
328.2 
390.5 


Grams. 

10.0 

499.0 


Grams. 

1, 585. 9 

587.6 


Grams. 
47.8 
111.0 


Calories. 
8,583 
9,306 


181 


Milk 




Total 








718.7 


509.0 


2, 173. 5 


158.8 


17, 889 




Feces (water free) 






197 


267.7 


58.0 
11.7 


17.2 


135.1 
11.7 


57.4 


1,116 




Estimated feces from food other 
than bread 




Estimated feces from 
bread 














46.3 




123.4 








Total amount digested 














660.7 
281.9 


491.8 


2, 038. 4 
1,462.5 


101.4 


16, 773 




Estimated digestible nutrients 
in bread 






Coefficients of digestibility of 
total food 












Per cent. 


Per cent. 
91.9 

85.9 


Per cent. 
96.6 


Per cent. 
93.8 

92.2 


Per cent. 
63.9 


Per cent. 
93 8 




Estimated coefficients of diges- 
tibility of bread 




«90 3 




Proportion of energy actually 
available to body: 
In total food 








89 2 




In bread alone 










« 86 2 















a Estimated on the assumption that 90 per cent of the fat in the bread is digestible. 



26 

During this experiment the subject eliminated 6,385 grams urine, 
containing 107.13 grams nitrogen. The average nitrogen balance per 
day was therefore as follows: Income in food, 30.01 grams; outgo in 
urine, 26.78 grams, and in feces, 2.32 grams, implying a gain of 0.91 
grams nitrogen, corresponding to 5.7 grams protein. 

DIGESTION EXPERIMENT NO. 248. 

Kind of food. — Milk, and bread made from straight patent flour. 

Subject. — University student No. 1. 

Weight. — At the beginning of experiment, 164 pounds; at the close, 
164 pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
May 1, 1901. 

Table 12. — Results of digestion experiment No. 248. 



Sample 
No. 




Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


199 


Food consumed: 

Bread 


Grams. 
2, 575. 
10, 583. 


Grams. 
248. 
321.7 


Grams. 

1.0 

404.3 


Grams. 

1,314.9 

509.0 


Grams. 
12.9 

78.3 


Calories. 
6,680 


198 


Milk 


7,715 




Total 








569.7 


405.3 


1, 823. 9 


91.2 14.395 


213 


Feces (water free) 








152.0 


45.5 
9.6 


26.5 
20.2 


38.0 
10.2 


41.9 


717 




Estimated feces from food other 


309 




Estimated feces from 












35.9 




27.8 








Total amount digested 














524.2 
212.1 


378. 8 1 - 785. 9 


49.3 


13, 678 




Estimated digestible nutrients 




1,287.1 


















Coefficients of digestibility of 
total food 


Per cent. 


Per cent. 
92.0 

85.5 


Per cent. 
93.5 


Per cent. 
97.9 

97.9 


Per cent. 
54 1 


Per cent. 
95.0 




Estimated coefficients of digest- 




a 94. 8 




Proportion of energy actually 
available to body: 








90.5 
















a 90. 9 



















a Estimated on the assumption that 90 per cent of the fat in bread is digestible 

During this experiment the subject eliminated 4,378 grams urine, 
containing 85.44 grams nitrogen. The average nitrogen balance per 
day was therefore as follows: Income in food, 23.79 grams; outgo in 
urine, 21.38 grams, and in feces, 1.82 grams, implying a gain of 0.59 
gram nitrogen, corresponding to 3.7 grams protein. 

DIGESTION EXPERIMENT NO. 249. 

Kind of food. — Milk, and bread made from straight patent flour. 

Subject. — University student No. 2. 

Weight.— At the beginning of the experiment, 152 pounds; at the 
close, 151^ pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
May 1, 1901. 



27 



Table 13. — Results of digestion experiment No. 249. 



Sample 

No. 




Weight 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


199 


Food consumed: 


Grams. 

2,790.0 

11, 717. 


Grams. 
268.7 
356.2 


Grams. 

1.2 

447.6 


Grams. 

1, 424. 6 

563.6 


Grams. 
13.9 
86.7 


Calories. 
7,237 


198 


Milk 


8,542 




Total 








624.9 


448.8 


1,988.2 


100.6 


15, 779 










214 




146.8 


41.9 
10.7 


16.8 


38.8 
11.3 


49.3 


626 




Estimated feces from food other 






Estimated feces from 















31.2 




27.5 








Total amount digested 















583.0 
237.5 


432.0 


1, 949. 4 
1, 397. 1 


51.3 


15, 153 




Estimated digestible nutrients 








Coefficients of digestibility of 
total food 












Per cent. 


Per cent. 
93.3 

88.4 


Per cent. 
96.3 


Per cent. 
98.1 

98.1 


Per cent. 
51.0 


Per cent. 
96.0 




Estimated coefficients of digest- 




a 95. 5 




Proportion of energy actually 
available to body: 
In total food 








91.4 














a 91. 4 






1 


1 







a Estimated on the assumption that 90 per cent of the fat in the bread is digestible. 

During this experiment the subject eliminated 7,846 grams urine, 
containing 77.52 grams nitrogen. The average nitrogen balance per 
day was therefore as follows: Income in food, 26.05 grams; outgo in 
urine, 19.38 grams, and in feces, 1.68 grams, implying a gain of 4.99 
grams nitrogen, corresponding to 31.2 grams protein. 

DIGESTION EXPERIMENT NO. 250. 

Kind of food. — Milk, and bread made* from straight patent flour. 

Subject. — University student No. 3. 

Weight. — At the beginning of the experiment, 152 pounds; at the 
close, 155 pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
May 1, 1901. 



Table 14. — Results of digestion experiment A r o. 250. 



Sample 
No. j 


Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


217 


Food consumed: 

Bread 


Grams. 
3, 080. 
13, 055. 


Grams. 
300.0 
441.3 


Grams. 

8.0 

541.8 


Grams. 

1, 605. 3 

596.6 


Grams. 
15.7 
99.2 


Calories. 
8,152 
9,713 


'216 


Milk 




Total 






741.3 


549.8 


2,201.9 


114.9 


17, 865 




Feces (water free) 




215 


167.0 


40.0 
13.2 


15.5 


60.9 
11.9 


50.6 


Til 




Estimated feces from food other 
than bread 




Estimated feces from 
bread 














26.8 




49.0 








Total amount digested 















701.3 
273. 2 


534.3 


2, 141. 
1, 556. 3 


64.3 


17,088 




Estimated digestible nutrients 
in bread 








===== 








28 



Table 14. — Results of digestion experiment No. 250 — Continued. 



Sample 

No. 




Weight 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 




Coefficients of digestibility of 
total food 


Per cent. 


Per cent. 
94.6 

91.1 


Per cent. 
97.2 


Per cent. 
97.2 

97,0 


Per cent. 
56.0, 


Per cent. 
95.7 




Estimated coefficients of diges- 
tibility of bread 




« 94. 5 




Proportion of energy actually 
available to body: 
In total food 








90.8 




In bread alone 












«90.3 



















a Estimated on the assumption that 90 per cent of the fat in the bread is digestible. 

During this experiment the subject eliminated 6,439 grams urine, 
containing 94.25 grams nitrogen. The average nitrogen balance per 
day was therefore as follows: Income in food, 30.76 grams; outgo in 
urine, 23.56 grams, and in feces, 1.60 grams, implying a gain of 5.60 
grams nitrogen, corresponding to 35.0 grams protein. 



SUMMARY OF RESULTS OBTAINED WITH HARD SPRING WHEAT 

PRODUCTS. 

The following tables summarize the results of the digestion experi- 
ments with hard spring wheat products reported in the foregoing pages. 
The results are given for the whole ration in Table 15 and computed 
for the different sorts of bread alone in Table 16. For purposes of 
comparison, the results obtained in previous experiments in this 
laboratory are also included, as well as the average digestibility of 
the different kinds of bread as shown by the result of all the 
experiments. 

Table 15. — Summary of digestion experiments with hard spring wheat; digestibility of 
nutrients and availability of energy of total food. 



Experi- 
ment 
No. 


Subject 

No. 


Kind of food. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Energy. 


242 


1 
2 
3 

1 
2 
3 

1 
2 
3 




Per cent. 
90.1 
92.6 
93.5 


Per cent. 
93.2 
97.2 
97.2 


Per cent. 
96.6 
96.9 
96.4 


Per cent. 
89.2 


243 


do 


90.7 


244 


do 


90.4 










92.1 
89.7 
90.9 


95.9 
91.7 
93.8 


96.6 
95.1 

95.8 


90.1 




Average of 3 (1899-1900) 


88.5 






89.3 








245 


89.1 
90.0 
91.9 


93.8 
96.6 
96.6 


92.6 
93.2 
93.8 


87.2 


246 


do.... 


88.6 


247 


...do 


89.2 










90.3 

88.2 
89.3 


95.7 
91.1 
93.4 


93.2 
91.1 
92.2 


88.3 




Average of 3 (1899-1900) 


86.0 






87.2 




Milk and white bread (standard patent) ... 
do 




248 
249 


92.0 
93.3 
94.6 


93.5 
96.3 
97.2 


97.9 
98.1 
97.2 


90.5 
91.4 


250 


..do 


90.8 










93.3 
91.4 
92.4 


95.7 
92.4 
94.5 


97.7 
97.6 
97 7 


90.9 




Average of 3 (1899-1900) 


90.3 






90.6 









29 

Table 16. — Summary of digestion experiments with hard spring wheat; digestibility of 
nutrients and availability of energy of bread alone. 



Experi- 
ment 
No. 


Subject 
No. 


242 


1 


243 


2 


244 


3 


245 


1 


246 


2 


247 


3 


248 


1 


249 


2 


250 


3 



Kind of food. 



Entire wheat bread 

....do 

....do 



Average of 3 

Average of 3 (1899-1900) 
Average of 6 



Graham bread . 

....do 

....do 



Average of 3 

Average of 3 (1899-1900) 
Average of 6 



White bread (standard patent). 

do 

....do 



Average of 3 r 

Average of 3 (1899-1900) 
Average of 6 



Protein. 



Per cent. 
83.4 
86.5 



86.2 
80.4 
83.3 



81.1 
81.5 
85.9 



82.8 
77.6 
80.2 



Carbo- 
hydrates. 



Per cent. 
96.2 
96.5 
95.9 



85.5 
88.4 
91.1 



88.3 
85.3 



96.2 
94.1 
95.1 



90.9 
91.4 
92.2 



91.5 

88.4 
90.0 



97.9 
98.1 
97.0 



97.7 
97.5 
97.6 



Energy. 



Per cent. 
89.1 
90.0 
90.2 



85.5 



83.9 
85.1 
86.2 



85.1 
80.7 
82.9 



91.4 
90.3 



90.9 
90.1 
90.5 



It will be observed that the average coefficients of digestibility of 
the protein and carbohydrates and of the available energy in the 
ration consisting of milk and bread made from straight patent flour 
ground from hard spring wheat were larger than in the rations of milk 
and entire-wheat bread or milk and graham bread from the same lot 
of wheat. Considering the calculated results for bread alone, in the 
experiments here reported it appears that in the graham bread the 
average digestibilit}^ of the protein is 82.8 per cent; of the carbohy- 
drates, 91.5 per cent, and the available energy is 85.1 per cent. The 
digestion coefficients for the graham bread are lower than for either 
the entire-wheat bread or the straight patent flour bread. In the case 
of the bread from en tire- wheat flour 86.2 per cent of the protein was 
digested, and in the straight patent flour bread 88.3 per cent, while 
96.2 per cent of the carbohydrates in the entire-wheat flour bread and 
97.7 per cent of those in the bread from the straight patent flour were 
found to be digestible. 

An examination of the tables also shows in each of the series a range 
of from 4 to nearly 6 per cent in the digestion coefficients of each of 
the nutrients. This is probably due to differences in the digestive 
powers of the three subjects. Thus, for example, subject No. 3 
digested the bread made from straight patent flour, en tire- wheat 
flour, and graham flour more completely than either subject No. 1 or 
No. 2. While individual differences are observed in the three series 
of experiments, in every case it appears that each subject digested 
the nutrients in the straight patent flour bread more completely than 
the nutrients in either the entire- wheat bread or the graham bread. 



30 

Hence the results for the average digestibilit}" in the different series 
of experiments are strictly comparable. 

The tables also compare the results of the experiments reported in 
this bulletin and those formerly reported. a It will be observed that 
although the digestion coefficients are somewhat larger in the experi- 
ments here reported than in those of 1899-1900, there is a general 
similarity of results. In both series the nutrients of the bread from 
standard patent flour are the most and those of graham the least 
digestible, the entire-wheat flour bread being between the two. These 
experiments are regarded as strictly comparable. Considering the 
two years' investigations as a whole, six subjects were empk^ed and 
eighteen separate digestion experiments were made. 

Table 16 gives the average digestibility of the nutrients and availa- 
bility of the energy in the three kinds of bread as shown by the results 
of the two series. It is believed that these figures show, with a fair- 
degree of accurac} T , the comparative digestibility of the protein and 
carbohydrates and availability of energy In bread made from the three 
kinds of flour when milled from the same lot of hard spring wheat 
and consumed under similar conditions. The results, considered as 
a whole, show that the protein in the straight patent flour bread is 
6.6 per cent more digestible than that of the graham bread, while the 
carbohydrates are 5.6 per cent more digestible. The amount of avail- 
able energ} 7 in the straight-flour bread is also greater by 7.5 per cent 
than that in the graham bread. 

In Table IT the total and digestible protein and carbohydrates and 
total and available energ} r in the three different kinds of flour as milled 
are given. These values for digestible nutrients and available energy 
were obtained by multiplying the percentage of total nutrients and 
energy by the coefficients given in Table 17. 

Table 17. — Percentages of digestible protein and carbohydrates, and available energy in 
entire-wheat, graham, and straight patent fours as milled. 



Grade of flour from hard spring wheat. 



Protein (Nx5.70). 



Di bi e e Sti " 



Carbohydrates. 



D tt 



Energy per gram. 



Total. 



Avail- 
able. 



Straight patent 
Entire wheat . . 
Graham 



Per cent. 
13.60 
13.72 
14.21 



Per cent. 
12.01 
11.83 
11.77 



Per cent. 
72.04 
70.09 
68.55 



Per cent. 
70.31 
67.43 
62. 62 



Per cent. 
3.861 
3.877 
3.971 



Per cent. 
3. 510 

3. 481 
3.379 



There was a somewhat larger amount of digestible protein in the 
straight patent flour than in either the graham or entire- wheat flour. 
In the straight patent flour there was 70.31 per cent of digestible 
carbohydrates, in the entire-wheat flour 67.-13 per cent, and in the 



oTJ. S. Dept. Agr., Office of Experiment Stations Bui. 101, p. 33. 



31 

graham flour 62.62 per cent; that is, the carbohydrates of the straight 
patent flour were much more digestible than those of either the entire 
wheat or graham flour. The amount of available energy of the straight 
patent flour is also larger than that of either the graham or entire- 
wheat flour. 

On comparing the figures in this table with those previously reported 
it will be observed that the results for protein here given are higher. 
This is due to two facts already pointed out, namely, that the per- 
centage of protein in the wheat employed in these experiments was 
higher, and the coefficients of digestibility were larger. The signifi- 
cance of the results, however, is the same in both cases. Briefly stated, 
the results of all of the experiments with hard spring wheat show that 
the digestible protein and carbohydrates, as well as the amount of 
available energy, are greater in the standard patent flour than in either 
the graham or entire-wheat flour. 

No marked variations in the balance of income and outgo of nitrogen 
were observed in the different periods except such as were due to 
differences in the amounts consumed. In other words, judged by the 
data regarding the metabolism of nitrogen, the three sorts of breads 
served the body equally well. 

The results of these experiments confirm those of earlier work with 
hard-wheat flours, and show that when breads made from straight 
patent flour, entire- wheat flour, and graham flour, milled from the 
same lot of hard spring wheat, are fed under uniform experimental 
conditions to men, there is a larger amount of digestible protein and 
carbohydrates and available energy in the patent flour than in either 
the entire- wheat or graham flour, although judged by composition the 
graham flour contains the most and the patent flour the least total 
protein. The greater digestibility of the protein and carbohydrates 
of the patent flour is regarded as due in part at least to the fineness 
of division of the flour particles, or, in other words, to the fact that a 
considerable portion of the nutrients in the graham and entire-wheat 
flours are present in comparatively large particles, which resist the 
action of the digestive fluids and so escape digestion. It has also been 
suggested that the cell walls in the layer of the grain directly under 
the bran are more resistant to digestive juices than the walls of cells in 
the interior of the kernel (see pp. 48, 49). Thus while there is actually 
somewhat more protein, pound for pound, in graham or entire-wheat 
than in patent flour, the body obtains less protein and energy from 
the coarser than it does from the finer flour, and whatever is gained 
in composition by adding the bran or germ is offset by the loss in 
digestibility. 



U. S. Dept. Agr., Office of Experiment Stations Bui. 101, p. 33. 



32 

DETAILS OF THE DIGESTION EXPEEIMENTS WITH BEEAD FROM 
DIFFERENT GRADES OF SOFT WINTER WHEAT FLOUR. 

In order to determine whether the results obtained with bread from 
hard-wheat flours would be the same with flours from wheat of a dif- 
ferent character, fifteen digestion experiments were made with bread 
from graham, entire-wheat, and standard patent flours milled from soft 
winter wheat. The results of these experiments are reported on the 
following pages. 

Two sets of experiments were made. In one set, comprising the 
first six of the following experiments, the flours used were prepared 
from the same lot of Indiana soft winter wheat by a milling company 
of Goshen, Ind. Only two kinds of flour were used in these six experi- 
ments, one being a standard patent grade similar to but not quite the 
same as the same grade of flour used in the experiments with hard 
wheat; the other was a so-called entire-wheat flour, but was somewhat 
coarser than this grade of flour prepared from hard wheat. In the 
second set of experiments three grades of flours were used, all ground 
from the same lot of Michigan soft winter wheat by a milling company 
of North Lansing, Mich. 

The experiments were made by the same methods as were followed 
in earlier work with hard-wheat flours. The experiment proper was 
preceded by a preliminary meal of bread and milk, charcoal being used 
to mark the separation of the feces. The experimental period con- 
tinued three days in the experiments with the Indiana flours, and four 
days with the Michigan flours. The subjects were young men in good 
health, designated as Nos. 1, 2, and 3. They were employed at farm 
labor, office, and university work. One subject, No. 1, had been 
employed in the digestion work of 1900 and 1901 as subject No. 3. 
The subjects were allowed a diet of bread and milk, unrestricted as to 
amount, the quantities consumed at each meal being carefully weighed. 
The different series of experiments in which graham, entire-wheat, 
and straight-grade flours were used were alike in all respects except 
as regards the bread. The four days' diet of milk and graham bread 
proved to be rather laxative. It was observed that the subjects who 
were employed at the severest labor had a decided preference for the 
bread made from the straight and mixed grade flours, while the one 
employed at office and university work did not have so pronounced a 
preference. In no case was the graham bread preferred. 

Tables 18 to 32 record the data of the several digestion experiments. 

DIGESTION EXPERIMENT NO. 309. 

Kind of food. — Milk, and bread made from straight-grade flour. 
Subject. — Man No. 1; age, 25 } 7 ears; employed at office work. 
Weight.— At the beginning of the experiment, 161.25 pounds; at 
the close, 162 pounds. 



33 



Duration. — Three days, with nine meals, beginning with breakfast 
April 9, 1902. 

Table 18. — Results of digestion experiment No. 309. 



Sample 
No. 


Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


[ Heat of 
Ash. combus- 
1 tion. 


223 
224 


Food consumed: 

Bread 

Milk 

Total 


Grams. 

2, 950. 
9, 850. 


Grams. 
236. 3 
326.0 


Grams. 

17.7 
431. 4 


Grams. 

1,513.9 
445. 2 


Grams. Calories. 
15.0 7,994 
77.8 ! 7,683 






562.3 


449.1 


1, 959. 1 


92.8 > 15,677 




Feces (water free) " 

Estimated feces from food other 






225 


166.0 


23.4 
9.8 


28. 3 
21. 6 


74.9 


39.4 ) 835 
347 




Estimated feces from 
bread 

Total amount digested 

Estimated digestible nutrients 
in bread 

Coefficients of digestibility of 
total food 










13. 6 


6.7 


66.0 




488 










538.9 
222. 7 


420.8 
11.0 


1. 884. 2 
1,447.9 


. 53. 4 14, 842 
7,506 




Per cent. 


Per cent. 
95.8 

94.2 


Per cent. 
93.7 

62.1 


Per cent. 
96.2 

95.6 


Per cent. , Per cent. 
57.5 




Estimated coefficients of diges- 






93.9 




Proportion of energy actually 
available to body: 






90.4 










90.4 






1 





During this experiment the subject eliminated 6,023 grams urine, 
containing 66.25 grams nitrogen. The nitrogen balance per day was 
therefore as follows: Income in food, 31.20 grams; outgo in urine, 
22.08 grams, and in feces, 1.25 grams, implying a gain of 7.87 grams 
nitrogen, corresponding to 19.2 grams protein. 

DIGESTION EXPERIMENT NO. 310. 

Kind of food. — Milk, and bread made from straight-grade Hour. 

Subject. — Man No. 2; age. 25 years; university student; employed 
at average farm labor four hours per day. 

Weight. — At the beginning and close of the experiment. 163.75 
pounds. 

Duration. — Three days, with nine meals, beginning with breakfast 
April 9, 1902. 

Table 19. — Results of digestion experiment Xo. 310. 



Sample 
Xo. 




Weight 

of 
material. 


Protein. 


v . lt i Carbo- A , 
Fat - ! hydrates. Ash ' 


Heat of 
combus- 
tion. 


223 


Food consumed: 

Bread 


Grams. 

2, 860. 
7, 850. 


Grams. 
229.0 
'259. 8 


Grams. ' Grams. 

17.2 1,467.7 

343.8 i 354.8 


Grams. 
14.6 
62.0 


Calories. 
7, 751 


224 


Milk ..; 


6, 123 




Total 








488.8 


361.0 | 1,822.5 


76.6 


13, 874 




Feces (water free) 




226 


147.0 


23.3 ; 57.2 
17.2 ! 7.1 


34.4 


779 




Estimated feces from food other 
than bread 




7.8 


287 




Estimated feces from 
bread 












24.3 


6 1 50.1 




492 















19017— Xo. 126—03- 



34 



Table 19. — Results of digestion experiment No.. 310 — Continued. 



Sample 

No. 



I Weight 

of Protein, 

material. 



Fat. 



Carbo- 
hydrates. 



Ash. 



Heat of 
combus- 
tion. 



Total amount digested 

Estimated digestible nutrients 
in bread . 



Grams. 



Grams. 
456. 7 



Grams. 
337.7 



Grams. 
1, 765. 3 



Gra?ns. Calories. 
42.2 13,095 



,259 



Coefficients of digestibility of Per cent. 

total food 

Estimated coefficients of diges- 
tibility of bread 

Proportion of energy actually 
available to body: • 

In total food 

In bread alone 



Per cent, i Per cent. 
93.4 93.5 



.4 i 



64.4 



Per cent. Per cent. 
55.1 



96.6 



Per cent. 
94.4 



93.6 



90.3 
90.4 



During this experiment the subject eliminated 4,296 grams urine, 
containing 64.61 grams nitrogen. The nitrogen balance per day was 
therefore as follows: Income in food, 27.25 grams; outgo in urine, 
21.54 grams, and in feces, 1.71 grams, implying a gain of 4 grams 
nitrogen, corresponding to 25 grams protein. 

DIGESTION EXPERIMENT NO. 311. 

Kind of food. — Milk, and bread made from straight-grade flour. 

Subject. — Man No. 3; 21 years of age, employed at average farm 
labor. 

Weight. — At the beginning of the experiment, 151.75 pounds; at the 
close, 150.5 pounds. 

Duration. — Three days, with nine meals, beginning with breakfast 
April 9, 1902. 

Table 20. — Results of digestion experiment No. 811. 



Sample 
No. 


Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


223 


Food consumed: 

Bread 


Grams. 
2, 572. 
6, 771. 


Grams. 
206.0 
224.1 


Grams. 

15.4 

296.6 


Grams. 

1,319.9 

306.1 


Grams. 
13.1 
53.5 


Calories. 
6,970 


224 


Milk 


5,281 




Total 








430.1 


312. 


1,626.0 


66.6 


12, 251 




Feces (water free ) 






Tin 


156.0 


41.7 
6.7 


14.2 


61.5 
6.! 


38.6 


686 




Estimated feces from food other 






Estimated feces from 














35.0 




55.4 








Total amount digested 














388.4 
171.0 


297.8 


1, 564. 5 
1, 264. 5 


28.0 


11,565 




Estimated digestible nutrients j 


















Coefficients of digestibility of 
total food 


Per cent. 


Per cent. 
90.3 

83.0 


Per cent. 
95.5 


Per cent. 
96.2 

95.8 


Per cent. 
42.0 


Per cent. 
94.4 




Estimated coefficients of digest- 




a 93. 5 




Proportion of energy actually 
available to body: 








90.4 











a 90. 4 








1 





a Calculated according to the assumption that 90 per cent of the fftt in the bread is digestible. 



35 

During this experiment the subject eliminated 4,486 grams urine, 
containing 58.77 grams nitrogen. The nitrogen balance per day was 
therefore as follows: Income in food 24 grams; outgo in urine 19.59 
grams, and in feces 223 grams, implying a gain of 2.18 grams nitrogen, 
corresponding to 13.6 grams protein. 

DIGESTION EXPERIMENT NO. 312. 

Kind of food. — Milk, and bread made from finely ground graham 
or entire-wheat flour. 

Subject. — Man No. 1, as in experiment No. 309. 

Weight. — At the beginning of the experiment 163.75 pounds; at the 
close 164 pounds. 

Duration. — Three days with nine meals, beginning with breakfast 
April 14, 1902, 

Table 21. — Results of digestion experiment No. 312. 



Sample 
No. 


Weight 

of 

, material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


231 
232 


Food consumed: 

Bread 

Milk 


Grams. 
3, 110. 
9, 500. 


Grams. 
265.3 
315.4 


Grams. 

31.7 

443.6 


Grams. 

1, 539. 1 

444.6 


Grams. 
45.4 
73.1 


Calories. 
8,210 
7,723 




Total 






580.7 


475.3 


1, 983. 7 


118.5 


15, 933 








233 


Feces (water free) 


260. 3 


37.3 
9.4 


13.9 


157.4 

8.9 


51.7 i 1.130 




Estimated feces from food other 








Estimated feces from 
bread 














27.9 




148.5 








Total amount digested 














543.4 
237.4 


461.4 




1,826.3 
1,390.6 


66.8 


14, 803 




Estimated digestible nutrients 
in bread 








Coefficients of digestibility of 
total food 














Per cent. 


Per cent. 
93.6 

89.5 


Per cent. 
97.1 


Per cent. 
92.1 

90.3 


Per cent. 
56.4 


Per cent. 
92.9 




Estimated coefficients of digest- 
ibility of bread 




«90.2 




Proportion of energy actually 
availabletobody: 
In total food 








88.6 




In bread alone 












«85.2 

















« Calculated according to the assumption that 90 per cent of the fat in the bread is digestible. 

During this experiment the subject eliminated 5,201.7 grams urine, 
containing 68.23 grams nitrogen. The total nitrogen balance per day 
was therefore as follows: Income in food, 32.34 grams; outg. in urine, 
22.74 grams, and in feces, 1.95 grams, implying a gain of 7.65 grams 
nitrogen, corresponding to 47.8 grams protein. 

DIGESTION EXPERIMENT NO. 313. 

-Kind of food. — Milk, and bread made from finely ground graham 
or entire-wheat flour. 

Subject. — Man No. 2, as in experiment No. 310. 

Weight. — At the beginning of the experiment, 164.5 pounds; at the 
close, 164.75 pounds. 



36 



Duration. — Three days, with nine meals, beginning with breakfast 
April 14, 1902. 

Table 22. — Results of digestion experiment No. 313. 



Sample 
No. 


Weight 
of 

material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


231 


Food consumed: 

Br^ad 


Grams. 

3. 070. 
9,770.0 


Grams. 
261.9 
324.4 


Grams. 

31.3 

456. 3 


Grams. 

1, 519. 3 

457. 2 


Grams. 
44. S 
75. 2 


Calories. 
8 105 


232 


Milk 

Total 


7,943 






586. 3 


487.6 


1,976.5 


120. 


16, 048 




Feces (water free) 




234 


294. 


49.3 
9.7 


30.3 

22.8 


164.6 
9.2 


49.8 


1,299 
319 




Estimated feces from food other 
than bread 




Estimated feces from 
bread 

Total amount digested 












7.5 


155. 4 




980 






537. 
222. 3 


457. 3 
23. 8 


1,811.9 
1, 363. 9 


70.2 


14. 749 




Estimated digestible nutrients 
in bread 





"/,125 



Coefficients of digestibility of Percent. Per ant. Percent. Percent. Per cent. Per cent. 



total food. 
Estimated coefficients of di- 
gestibility of bread 

Proportion' of energy actually 
available to body: 

In total food 

In bread alone 



84.9 



93.8 

7e.o 



91. 
89i8 . 



58. 5 



91.9 



84.5 



During this experiment the subject eliminated 5,201.7 grams urine, 
containing 73.35 grams nitrogen. The total nitrogen balance per day 
was therefore as follows: Income in food, 32.62 grams; outgo in urine, 
24.15 grams, and in feces, 2.60 grams, implying a gain of 5.57 grams 
nitrogen, corresponding to 34. S grams protein. 

DIGESTION EXPERIMENT NO. 314. 

Kind of food. — Milk, and bread made from finely ground graham 
or entire-wheat flour. 

Subject. — Man No. 3, as in experiment No. 311. 

Weight. — At the beginning of the experiment, 150.5 pounds; at the 
close, 151 pounds. 

Duration. — Three days, with nine meals, beginning with breakfast 
April 14, 1902. 

Table 23. — Results of digestion experiment No. 314-' 



Sample 
No. 






-Weight 

of 
material. 


Protein, 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


231 
232 


Food consumed: 

Bread 

Milk 

Total 




Grams. 

2, 670. 

8, 000. 


Grams. 

227. 7 
265. 6 


Grams. 

27 2 
373." 6 


Grams. 

1,321.4 
374.4 


Grams. 

39.0 
61.6 


Calories. 

7,049 
6,504 






493. 3 


400.8 


1.695.8 


100.6 


13, 553 


235 


275. 


55. 2 

S.O 


11.9 


155. 4 
7.5 


52.6 


1,144 




Estimated feces from food other 






Estimated feces 
bread 


from 












1 


47.2 





147.9 
















37 



Table 23. — Results of digestion experiment No. 314 — Continued. 



Sample 
No. 



Weight 

of 
material. 



Protein. 



Fat. 



1 Carbo- 
hydrates. 



Ash. 



Total amount digested 

Estimated digestible nutrients 
in bread 



Gram*. 
438. 1 



180. 5 



Grams. 
388.9 



Grams. 
1,540.4 



Grams. 
48.0 



Heat of 
combus- 
tion. 



Calories. 
12, 409 



Coefficients of digestibility of 

total food 

Estimated coefficients of diges- 
tibility of bread 

Proportion of energy actually 
available to body: 

In total food 

In bread alone 



Per cent. \ Per cent. Per cent. 
88.8 i 97.0 



Per cent. 
90.8 



Per cent. 

47.7 



79.3 



Per cent. 
91.6- 



a 86. 1 



87. o 

a 82. 9 



« Calculated according to the assumption that 90 per cent of the fat in the bread is digestible. 

During this experiment the subject eliminated 4,115.6 grams urine, 
containing 60.91 grams nitrogen. The total nitrogen balance per day 
was therefore as follows: Income in food, 27.18 grams; outgo in urine, 
20.30 grams, and in feces, 2.91 grams, implying a gain of 4.24 grams 
nitrogen, corresponding to 26.5 grams protein. 

DIGESTION EXPERIMENT NO. 315. 



Kind of food. — Milk, and bread made from straight iiour. 
Subject. — Man No. 1, as in experiment No. 309. 
Weight. — At the beginning and close of the experiment, 166 pounds. 
Duration.— Your days, with twelve meals, beginning with breakfast 
April 28, 1902. 

Table 24. — Results of digestion experiment Xo. 315. 



Sample 
No. 


i Weight 
1 of 
; material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


244 
243 


Food consumed: 

Bread 

Milk 

Total 


Grams. 
3,615.0 
ll,750.u 


Grams. 
274.4 
351. 3 


Grams. • 

13.7 

480.6 


Grams. 

1,976.3 

565. 2 


Grams. ' Calories. 
17.7 9,435 
90.5 ! 8,719 






625. 7 


494.3 


2,541.5 


108.2 ) 18,154 




Feces (water free) 






245 


132.0 


29.8 
10.5 


11.3 


58.1 
11.3 


32.8 667 




Estimated feces from food other 
than bread 






Estimatedfecesfrom bread 
Total amount digested 






! 






19.3 




16.8 
















595. 9 
255. 1 


483. 


2,483.4 
1 . 9'>Q. r> 


75.4 1 17,487 




Estimated digestible nutrients 
in bread 






Coefficients of digestibility of 
total food 




1 






Per cent. 


Per cent. 
95.2 

93.0 


Percent. 
97.7 


Per cent. 
97.7 

97.6 


Per cent. 
69.7 


Per cent. 
96.3 




Estimated coefficient of diges- 
tibility of bread 




(i97.3 




Proportion of energy actually 
available to body: 
In total food 




92 2 




In bread alone 












a 93. 4 













a Calculated according to the assumption that 90 per cent of the fat in the bread is digestible. 



38 

During this experiment the subject eliminated 7,317.4 grams urine, 
containing 87.08 grams nitrogen. The total nitrogen balance per day 
was therefore as follows: Income in food, 26.09 grams; outgo in urine, 
21.77 grams, and in feces, 1.19 grams, implying a gain of 3.13 grams 
nitrogen, corresponding to 19.6 grams protein. 

DIGESTION EXPERIMENT NO. 316. 

Kind of food. — Milk, and bread made from straight flour. 
Subject. — Man No. 2, as in experiment No. 310. 
Weight. — At the beginning and close of the experiment, 166 pounds. 
Duration. — Four days, with twelve meals, beginning with breakfast 
April 28, 1902. 

Table 25. — Results of digestion experiment No. 316. 



Sample 
No. 




Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


244 
243 


Food consumed : 

Bread 

Milk 

Total 


Grams. 
3,480.0 
12, 730. 


Grams. 
264.1 
380.6 


Grams. 

13.2 

520. 6 


Grams. 

1,902.3 

612.3 


Grams. 
17.0 
98.0 


Calories. 
9,082 
9,445 




C44.7 


533.8 


2, 514. 6 


115.0 


18, 527 




Feces ( water free ) 






113.0 


26.1 
11.4 


• 14.8 


44.0 
12.3 


28.0 


583 


246 


Estimated feces from food other 






Estimated feces from 
bread 

Total amount digested 

Estimated digestible nutrients 
in bread 

Coefficients of digestibility of 
total food ' 















14.7 




8X.7 


















618. 6 
249.4 


519. 


2, 470. 6 
1 870.6 


87.0 


17,944 












Per cent. 


Per cent. 
95.9 

94.4 


Per cent. 
97.2 


Per cent. 

98.2 

98. 3 


Per cent. 
75.6 


Per cent. 
96.9 




Estimated coefficients of di- 
gestibility of bread 




«98.5 




Proportion'of energy actually 
available to body : 
In total food. .*. 


\ 





92.7 




In bread alone • 






«95.1 




! i ! 









a Calculated according to the assumption that 90 per cent of the fat in the bread is digestible. 

During this experiment the subject eliminated 6,556.6 grams urine, 
containing 92.45 grams nitrogen. The total nitrogen balance per da} T 
was therefore as follows: Income in food, 26.81 grams; outgo in urine, 
23.11 grams, and in feces, 1.05 grams, implying a gain of 2.65 grams, 
nitrogen, corresponding to 16.6 grams protein. 

DIGESTION EXPERIMENT NO. 317. 

Kind of food. — Milk, and bread made from straight flour. 

Subject. — Man No. 3, as in experiment No. 311. 

Weight. — At the beginning of the experiment, 151 pounds; at the 
close, 150.25 pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
April 28, 1902. 



39 



Table 26. — Results of 



experiment -No. 317. 



Sample 

No. 


; Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


24 i 
243 


Food consumed: 

Bread 

Milk 


Grams. 

3, 330. 
10,150.0 


Grams. 
252.7 
303.5 


Grams. 

12.6 

415.1 


Grams. 

1, 820. 3 

488.2 


Grams. 
16.3 

78.2 


Calories. 
8,691 
7,531 




Total 




556.2 


427. 7 


2, 308. 5 


94.5 


16,222 











2-47 


127.0 


32.2 
9.1 


19.4 


41.4 
9 .8 


34.1 


681 




Estimated feces from food other 






Estimated feces from 














23.1 





31.6 








Total amount digested 














524.0 
229.6 


408.3 


2,267.1 
1, 788. 7 


60.4 


15, 541 




Estimated digestible nutrients 








Coefficients of digestibility of 
total food * 













Per cent. 


Per cent. 
94.2 

90.9 


Per cent. 
95.5 


Per cent. 
98.2 

98.2 


Per cent. 
63.9 


Per cent. 
95.8 




Estimated coefficientsof digest- 




a 97. 4 




Proportion of energy actually 
available to body: 








91.8 














a 94.1 










1 





a Calculated according to the assumption that 90 per cent of the fat in the bread is digestible. 

During- this experiment the subject eliminated 4,747.6 grams urine, 
containing 65.99 grams nitrogen. The total nitrogen balance per day 
was therefore as follows: Income in food, 23.22 grams; outgo in urine, 
16.50 grams, and in feces, 1.29 grams, implying a gain of 5.43 grams 
nitrogen, corresponding to 33.9 grams protein. 

DIGESTION EXPERIMENT NO. 318. 

Kind of food. — Milk, and bread made from entire-wheat flour. 

Subject. — Man No. 1, as in experiment No. 309. 

Weight. — At the beginning of the experiment, 167.25 pounds; at the 
close, 168 pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
Mav 5, 1902. 



Table 2\ 



■Results of digestion experiment No. 318. 



Sample' 

No. 


Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


251 
258 


Food consumed: 

Bread 

Milk 

Total 


Grams. 
3, 700. 
12, 000. 


Grams. 
308.2 
360.0 


Grams. 
40.0 
462.0 


Grams. 

1,913.0 

570.0 


Grams. 
47.0 
87.6 


Calories. 
9,952 
8,820 






668.2 


502. 


2, 483. 


134 fi 


18 772 




Feces ( water free) 








252 


287.0 


51.5 
10.8 


15.2 


161.5 
11.4 


58 8 i 9R1 




Estimated feces from food other 
than bread 








Estimated feces from 
bread 














40.7 




150 1 








Total amount digested 












616.7 
267.5 


486.8 


2, 321. 5 
1,762.9 


75.8 , 17 541 




Estimated digestible nutrients 
in bread 

















40 



Table 27. — Results of digestion experiment No. SIS — Continued. 



Sample 
No. 




Weight 

of 
material. 


Protein. 


|Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 




Coefficients of digestibility of Per cent. 


Per cent. 
92.3 

86.8 


Per cent. 
97.0 


Per cent. 
93.5 

92.2 


Per cent. 
56.3 


Per cent. 
93 4 




Estimated coefficients of digest- 
ibility of bread 


a 91. 3 




Proportion of energy actually 
available to body: 
In total food 






89.3 






1 






a 87. 9 




1 


1 




■ 





o Calculated according to the assumption that 90 per cent of the fat in the bread is digestible. 

During this experiment the subject eliminated 7,889.1 grams urine, 
containing 84.11 grams nitrogen. The total nitrogen balance for four 
da}^s was therefore as follows: Income in food, 27.92 grams; outgo in 
urine, 21.10 grams, and in feces, 2.06 grams, implying a gain of 4.76 
grams nitrogen, corresponding to 29.8 grams protein. 

DIGESTION EXPERIMENT NO. 319. 

Kind of food. — Milk, and bread made from entire- wheat flour. 

Subject. — Man No. 2, as in experiment No. 310. 

Weight. — At the beginning and close of the experiment, 167.5 
pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
May 5, 1902. 

Table 28. — Results of digestion experiment No. 319. 



Sample 
No. 




Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


251 

258 


Food consumed: 

Bread 

Milk 

Total 

Feces (water free) 


Grams. 

3, 655. 

12, 380. 


Grams. 
304.5 
371.4 


Grams. 

39.5 

476.6 


Grams. 

1, 889. 5 

588.0 


Grams. 
46.4 
90.4 


Calories. 
9,831 
9,100 







675.9 


516. 1 


2, 477. 5 


136.8 


18, 931 


253 


302.0 


63.4 

n. 


35.2 
23.8 


140.1 

11.8 


63.3 


1,332 




Estimated feces from food other 
than bread 


351 




Estimated feces from 












52.3 


11.4 


128. 3 




981 




Total amount digested 












612. 5 
252.2 


480.9 

28.1 


2, 337. 4 

1,761.2 


73.5 


17, 599 




Estimated digestible nutrients 
in bread 




8,850 




Coefficients of digestibility of 
total food 











Per cent. 


Per cent. 
90.6 

82.8 


Per cent. 
93.2 

71.1 


Per cent. 
94.3 

93.2 


Per cent. 
53.7 


Per cent. 
92.9 




Estimated coefficients of di- 




90.0 




Proportion of energy actually 
available to body: 






88.9 












! 


86.8 












1 





During this experiment the subject eliminated 6,910.1 grams urine, 
containing 101.58 grams nitrogen. The total nitrogen balance per day 
was therefore as follows: Income in food, 28.21 grams; outgo in urine, 



41 

25.39 grams, and in feces, 2.57 grams, implying a gain of 0.25 gram 
nitrogen, corresponding to 1.6 grams protein. 

DIGESTION EXPERIMENT NO. 320. 

Kind of food. — Milk, and bread made from entire-wheat flour. 

Subject. — Man No. 3, as in experiment No. 311. 

Weight. — At the beginning of the experiment, 150 pounds; at the 
close, 151.5 pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
May 5, 1902. 

Table 29. — Results of digestion experiment Xo. 320. 



Sample 
Xo. 


1 Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


251 
258 


Food consumed: 

Bread 

Milk 

Total 


Grams. 
3, 650. 
11, 750. 


Grams. 
304.0 
352.5 


Grams. 

39.4 

452.4 


Grams. 

1, 887. 1 

558.1 


Grams. 
46.3 

85.8 


Calories. 
9,818 
8,636 






656.5 


491.8 


2,445.2 


132.1 


18, 454 


254 


262. 


48.9 
10.6 


15.7 


135.6 

11.2 


61.7 


1,045- 




Estimated feces from food other 






Estimated feces from 
bread 

Total amount digested 












38.3 




124.4 














607.6 

265.7 


476.1 


2, 309. 6 
1, 762. 7 


70.4 


17,409 




Estimated digestible nutrients 






Coefficients of digestibility of 
total food 












Per cent. 


Per cent. 
92.5 

87.4 


Per cent. 
96.8 


Per cent. 
94.4 

93.4 


Per cent. 
53.3 


Per cent. 
94.3 




Estimated coefficients of di- 
gestibilitv of bread 




«92.7 




Proportion of energy actually 
available to body: 








90.2 












a 89. 4 




) 











a Calculated according to the assumption that 90 per cent of the fat in the bread is digestible. 

During this experiment the subject eliminated 5,476.6 grams urine, 
containing 88.17 grams nitrogen. The total nitrogen balance per day 
was therefore as follows: Income in food, 27.44 grams; outgo in urine, 
22.04 grams, and in feces 1.96 grams, implying a gain of 3.44 grams 
nitrogen, corresponding to 21.5 grams protein. 

DIGESTION EXPERIMENT NO. 321. 

Kind of food. — Milk, and bread made from graham flour. 

Subject. — Man No. 1, as in experiment No. 309. 

Weight. — At the beginning of the experiment, 169.75 pounds; at the 
close, 170 pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
May 16, 1902, 



42 



Table 30. — Results of digestion experiment No. 321. 



Sample 
No. 


- 


Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


260 


Food consumed: 


Grams. 

3, 695. 

11, 850. 


Grams. 
308.9 
385.1 


Grams. 

32.2 

527.3 


Grams. 

1, 891. 8 

596.1 


Grams. 

53.6 
91.2 


Calories. 
9,681 


259 


Milk 


9.207 




Total 








694.0 


559.5 


2, 487. 9 


144.8 ' 18,888 




Feces (water free) 






261 


389.0 


75.9 
11.6 


25.1 


222.0 
11.9 


66. 1 1, 641 




Estimated feces from food other 
than bread 


i 




Estimated feces from 












64.3 




210.1 


1 




Total amount digested 

Estimated digestible nutrients 












618.1 
244.6 


534.4 


2. 265. 9 
1, 681. 7 


78.7 


17, 247 




Coefficients of digestibility of 












Per cent. 


Per cent. 
89.1 

79.2 


Per cent: 
95.5 


Per cent. 
91.1 

88.9 


Per cent. 
54.4 


Per cent. 
91.3 




Estimated coefficients of diges- 




«85.8 




Proportion of energy actually 
available to body: 








87.2 




In bread alone 








a 82. 7 













a Calculated according to the assumption that 90 per cent of the fat in the bread is digestible. 

During this experiment the subject eliminated 5,211 grams urine, 
containing 73.48 grams nitrogen. The total nitrogen balance per day 
was therefore as follows: Income in food, 28.95 grams; outgo in urine, 
18.37 grams, and in feces, 3.04 grams, implying a gain of 7.54 grams 
nitrogen, corresponding to 47.1 grams protein. 

DIGESTION EXPERIMENT NO. 322. 

Kind of food. — Milk, and bread made from graham flour. 

Subject. — Man No. 2, as in experiment No. 310. 

Weight. — At the beginning and close of the experiment, 166.5 
pounds. 

Duration. — Four days, with twelve meals, beginning with break- 
fast May 16, 1902. 

Table 31. — Results of digestion experiment No. 322. 



Sample 
No. 




Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


260 


Food consumed: 

Bread 


Grams. 

3, 455. 

11,750.0 


Grams. 
288.8 
381.9 


Grams. 

30.1 

522.9 


Grams. 

1, 768. 9 

591.0 


Grams. 
50.1 
90.5 


Calories. 
9, 052 


259 


Milk 


9,130 




Total 








670.7 


553.0 


2, 359. 9 


140.6 


18, 182 




Feces (water free) 






262 


387.0 


69.1 
11.5 


54.1 
26.1 


197.9 
11.8 


65.9 


1,730 




Estimated feces from food other 
than bread 


361 




Estimated feces from 
bread 












57.6 


28.0 


186.1 




1,369 




Total amount digested 












601.6 
231.2 


498.9 
2.1 


2, 162. 
1,582.8 


74.7 


16,452 




Estimated digestible nutrients 
in bread 




7,683 













43 



Table 31. — Results of digestion experiment No. #££— Continued. 



Sample 

No. 




Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 




Coefficients of digestibility of 


Per cent. 


Per cent. 
89.7 

80.1 


Per cent. 
90.2 

7.0 


Per cent. 
91.6 

89.5 


Per cent. 
53.1 


Per cent. 
90.5 




Estimated coefficients of digest- 




84.9 




Proportion of energy actually 
available to body: 
In total food 




86.3 








' 




81.7 















During this experiment the subject eliminated 4,532 grams urine, 
containing 52.57 grams nitrogen. The total nitrogen balance per day 
was therefore as follows: Income in food, 27.94 grams; outgo in urine, 
13.14 grams, and in feces, 2.76 grams, implying a gain of 12.04 grams 
nitrogen, corresponding to 75.2 grams protein. 

DIGESTION EXPERIMENT NO. 323. 

Kind of food. — Milk, and bread made from graham flour. 

Subject. — Man No. 3, as in experiment No. 311. 

Weight. — At the beginning of the experiment, 151.25 pounds; at 
the close, 150.5 pounds. 

Duration. — Four days, with twelve meals, beginning with breakfast 
May 16, 1902. 

Table 32. — Results of digestion experiment No. 328. 



Sample 
No. 




Weight 

of 
material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


Ash. 


Heat of 
combus- 
tion. 


260 


Food consumed: 


Grams. 
3, 580. 
11, 000. 


Grams. 
299.3 
357.5 


Grams. 

31.1 

489. 5 


Grams. 

1,832.9 

553.3 


Grams. 
51.9 
84.7 


Calories. 
9,379 


259 


Milk 


8, 546 




Total 








656.8 


520.6 


2, 386. 2 


136.6 : 17,925 




Feces (water free) 






263 


384.0 


73.4 
10.7 


31.7 

24.5 


202.3 
11.1 


• 76. 6 1 - 601 




Estimated feces from food other 
than bread 




348 




Estimated feces from 










62. 7 


7.2 


191.2 




1,253 




Total amount digested 










583.4 
236.6 


488.9 
23.9 


2, 183. 9 
1,641.7 


60. 1 6. 324 




Estimated digestible nutrients 






8,126 




Coefficients of digestibility of 








Per cent. 


Per cent. 
88.8 
79.0 


Per cent. 
93.9 

76.8 


Per cent. 
91.5 
89.6 


Per cent. 
43.9 


Per cent. 
91.1 




Estimated coefficients of diges- 




86.6 




Proportion of energy actually 
available to body: 
In total food 






87.0 














83.5 

















During this experiment the subject eliminated 4,509 grams urine, 
containing 85.16 grams nitrogen. The total nitrogen balance per day 
was therefore as follows: Income in food, 27.42 grams; outgo in 



44 

urine, 21.29 grams, and in feces, 2.94 grams, implying a gain of 3.19 
grams nitrogen, corresponding to 19.9 grams protein. 

SUMMARY OF RESULTS OBTAINED WITH SOFT WINTER WHEAT 

PRODUCTS. 

In Table 33 a summary is given of the digestibilit}^ of the nutrients 
and availablity of the energy of the entire food of the various digestion 
experiments with milk and white bread from mixed-grade flour, white 
bread from straight-grade flour, entire-wheat bread, and graham, ail 
ground from soft winter wheat. 

Table 33. — Summary of digestion experiments with soft winter wheat; digestibility of 
nutrients and availability of energy of total food. 



Experi- 
ment 
No. 


Subject 
No. 


Kind of food. 


Protein. 


Fat, 


Carbo- 
hydrates. 


Energy. 


309 
310 


1 
2 

3 

1 
2 
3 

1 
2 
3 

1 

2 

. 3 

1 

2 
3 


Experiments with Indiana wheat: 

Milk and white bread (mixed grade) . . . 
do 


Per cent. 
95.8 
93.4 
90.3 


Per cent. 
93.7 
93.5 
95. § 


Per cent. 
96.2 
96.9 
96.2 


Per cent. 
90.4 
90.3 


311 


....do 


90.4 




Average of 3 






93. 2 


94.2 


96.4 


90.4 




Milk and entire- wheat bread 




312 


93.6 
91.6 

88.8 


97.1 
93.8 
97.0 


92.1 
91.7 
90.8 


8S.6 


313 


....do 


87.7 


314 


....do 


87.5 










91.3 


96.0 


91.5 


87.9 




Experiments with Michigan wheat: 

Milk and white bread (standard patent) 
do 




315 
316 


95.2 
95.9 
94.2 


.7.7 

97.2 
95. 5 


97.7 

98.2 
98.2 


92.2 
92.7 


317 


....do 


91.8 










95.1 


96.8 


98.0 


92.2 








318 


92.3 
90.6 
92.5 


97.0 
93.2 
96.8 


93.5 
94.3 
94.4 


89.3 


319 


....do 


88.9 


320 


....do 


90.2 










91.8 


95.7 


94.1 


89.5 








321 


89.1 
89.7 

88.8 


95.5 
90.2 
93.9 


91.1 

91.6 
91.5 


87.2 


322 
323 


do 

....do 


86.2 
. 87.0 




89.2 


93.2 


91.4 


86.8 









The results summarized in the table show that, in general, the ration 
consisting of milk and white bread made from the patent grade flour 
was more digestible than the rations of milk and bread made from 
either of the other kinds of flour, also that a larger percentage of 
energy was available to the body in the case of white bread and milk 
than from the entire-wheat or graham bread and milk. 

In the experiments with Indiana soft wheat individual differences as 
regards the ability to digest the bread and milk rations were quite 
pronounced with the various subjects; in the case of the white bread, a 
difference of about 5.5 per cent in the digestibility of the protein being- 
observed. Subject No. 1 digested the wheat bread and also the entire- 
wheat bread more completely than did subject No. 2 or No. 3. With 



45 

each subject, however, the digestibility of the ration with white bread 
was greater than that with entire wheat. In the experiments with 
Michigan soft wheat individual differences are noticeable, but they 
are less pronounced, and, as was the case with the other wheats, each 
subject digested the ration of white bread and milk more completely 
than bread made from either of the other flours. 

In Table 34 the calculated- digestibility of the nutrients and availa- 
bility of the energy of the bread alone are given: 

Table 34. — Summary of digestion experiments with soft winter wheat; digestibility of 
nutrients and availability of energy of bread alone. 



Experi- 
ment 
No. 



Subject 
No. 



Kind of food. 



Carbo- 



Protein. hydrates | Energy 



310 
311 



Experiments with Indiana wheat: 
White bread (mixed grade flour) 

do 

....do : 



cent. Per cent. : . Per cent. 

94.2 95.6 I 90.4 

89.4 96.6 j 90.4 

83. 95. 8 90. 4 





1 
2 
3 

1 
2 
3 

I 

3 

1 
2 

3 


Average of 3 


88.9 


96.0 


90.4 


312 


89.5 
84.9 
79.3 


90.3 

89.8 
88.8 


85. 2 


313 

314 


do 

....do 


84.5 
82.9 




84. 6 


89.6 


84.2 




Experiments with Michigan wheat: 




315 


93.0 
94.4 
90.9 


97.6 
9S.3 

98,2 


93.4 


316 
317 


do 

....do 


95.1 
94.1 




Average of 3 

Entire-wheat bread 






92.8 


98.0 


94.2 


318 


86. 8 

82.8 

87.4 


92.2 
93.2 

93.4 


87.9 


319 
320 


....do 

— do 


86.8 
89.4 




85.7 


92.9 


88.0 




Graham bread 




321 


79.2 
80.1 
79.0 


8S.9 
89.5 
89.6 


8°. 7 


322 
323 


....do 

....do 

Average of 3 


81.7 
83.5 




79.4 


89.3 


82.6 



These results are calculated, as explained on page 19. by assuming 
that 97 per cent of the protein and 98 per cent of the carbohydrates of 
the milk were digested. 

The average result of the experiments with flour milled from Indi- 
ana soft winter wheat shows that 88.9 per cent of the protein and 96 
per cent of the carbohydrates of the white bread from mixed-grade 
flour were digested, and that 90.4 per cent of the energy was available. 
As regards the bread from entire-wheat flour, ground from the same 
lot of wheat, 84.6 per cent of the protein and 89.6 per cent of the car- 



a It was also assumed that 95 per cent of the fat of the milk would be digested, but 
with this factor the digestibility of the fat of bread could be computed satisfactorily 
in only a few cases; therefore figures for this constituent are left out of Table 34. 
In all cases where the digestibility of bread fat could not be computed it was assumed, 
in order to estimate the available energy of the bread, that 90 per cent would be 
digested. 



46 

bohydrates were found to be digestible, and 84.2 per cent of the energy 
to be available. It will be observed, further, that with each of the sub- 
jects the nutrients of the white bread were more digestible and the 
energy more available than was the case with the entire- wheat bread. 

The white bread made from straight-grade flour milled from Michi- 
gan soft winter wheat had the highest digestibility of any of the sam- 
ples ground from this variety, namely, 92.8 per cent of the protein 
and 98 per cent of the carbohydrates, while 94.2 per cent of the energy 
was available to the body. Of the protein of bread from the entire- 
wheat flour milled from the same lot of wheat, 85.7 per cent, and of 
the carbohydrates 92.9 per cent were digestible, 88 per cent of the 
energy being available to the body. The lowest coefficients of digesti- 
bility were found in the graham bread, the values being 79.4 per cent 
for the protein, 89.3 per cent for the carbohydrates, and 82.6 per cent 
for the energy available to the body. As will be seen, there was a dif- 
ference of 13.4 per cent in the average digestibility of the protein of 
the graham bread and white bread made of flour from the same lot 
of wheat, while 8.7 per cent less of the carbohydrates of the graham 
bread was digestible, and 11.6 per cent less of the energy was avail- 
able. As in the case of the entire ration, differences attributable to 
individuality are noticeable, which are, however, not great enough to 
invalidate the general deduction that white bread is the most digesti- 
ble, graham bread the least, and entire-wheat bread intermediate 
between them. 

Table 35 gives a summary of the experiments on the basis of the pro- 
portion of total and digestible nutrients and available energy in the 
different grades of flour as milled from soft winter wheat: 

Table 35. — Proportion of total and digestible nutrients and available energy in different 
grades of soft winter-wheat flour as milled. 



Num- 
ber of 
sample. 


Grade of flour. 


Protein. 


Carbohydrates. 


Heat of combus- 
tion per gram. 


Total. 


Digest- 
ible. 


Total. 


Digest- 
ible. 


Total. 


Avail- 
able. 


221 




Per cent. 
12.30 
12.80 
10.92 
12.01 
12.24 


Per cent. 
10.93 
10.82 
10.13 
10.29 
9.72 


Per cent. 
75.94 
74.40 
77.15 
74.17 
73. 27 


Per cent. 
72.90 
66.66 
75.61 
68.80 
65.43 


Calories. 
4.010 
4.020 
3.799 
3.860 
3.906 


Calories. 
3.645 


219 


Entire-wheat flour 


3.384 


240 


Straight white flour 


3.579 


241 


Entire- wheat flour 


3.399 


242 


Graham flour 


3.22& 









The digestible nutrients were obtained by multiplying the percent- 
age of the total nutrients by the average digestion coefficients given 
in Table 34. The mixed-grade flour, for example, contained 12.3 per 
cent total protein, which was found to be 88.9 per cent digestible, 
being therefore equivalent to 10.93 per cent of digestible protein. 
The mixed-grade flour prepared from the Indiana wheat contained 
10.93 per cent digestible protein, 72.90 per cent digestible carbo- 



47 

hydrates, and 1 gram of the flour yielded 3.645 calories of available 
energy. The entire-wheat flour prepared from the same wheat yielded 
10.82 per cent digestible 'protein, 66.87 per cent digestible carbo- 
hydrates, and 3.375 available calories per gram. The difference in 
digestible protein is small, being 0.11 per cent in favor of the mixed- 
grade flour. The difference in the digestible carbohydrates is quite 
large, being 6.24 per cent in favor of the mixed-grade flour. The 
difference in the available energy is also large, amounting to 0.261 
calorie per gram in favor of the white flour. 

While there is no material difference as to the amount of digestible 
protein in the two kinds of flour, the differences in digestible carbo- 
hydrates and available energy are decidedly in favor of the mixed-grade 
flour. The entire-wheat flour contained a larger amount of protein, 
but, as shown in Table 34, this protein is less digestible than that of 
the mixed-grade flour, which was more finely granulated. 

The straight-grade flour prepared from the Michigan wheat con- 
tained 10.13 per cent digestible protein, 75.61 per cent digestible 
carbolrydrates, and 3.574 calories of available energy per gram. Com- 
pared with graham flour, this shows 0.4 per cent of digestible protein, 
10.18 per cent of digestible carbohydrates, and 0.353 calorie of avail- 
able energy per gram in favor of the white flour. Compared with 
the entire-wheat flour, the results show a difference of 6.81 per cent 
digestible carbohydrates and 0.180 available energy per gram in favor 
of the straight-grade flour; the difference in digestible protein, though 
too small to be of significance, is 0.16 per cent in favor of the entire- 
wheat flour. In the description of the samples it was stated that the 
straight-grade flour did not contain all of the granular middlings 
which are usualty included in the preparation of ordinary straight 
flours. Had the flour contained the granular middlings, the percent- 
age of protein, it seems fair to conclude, would have been higher than 
10.92. While the difference in total protein is 1.1 per cent in favor of 
the entire-wheat flour, the higher degree of digestibility of this con- 
stituent in the straight- grade flour makes the figures for the total 
digestible protein in the two kinds of flour practically the same. 
Hence, what is gained from the somewhat larger amount of protein in 
the entire- wheat and graham flours is lost in digestibilit} r . While the 
difference between the digestible protein in the straight-grade and 
entire-wheat flours prepared from the same lot of soft wheat is small, 
the difference in digestible carbohydrates is large, being 6.8 per cent 
in favor of the white flour. Since a larger amount of digestible carbo- 
hydrates and available energy is secured from the mixed and straight- 
grade flours than from the entire-wheat flour and no appreciable 
differences were observed as to digestible protein, it would appear 
that a larger total amount of nutrients and energy is available to the 



48 

body from the straight than from the entire-wheat or graham flours, 
a conclusion in accord with the results of all our former work. 

That the lower degree of digestibility of the entire-wheat and graham 
flours was probably due at least in part to a coarser granulation 
of the particles, which consequently exposed a relatively smaller 
amount of surface to the action of the digestive fluids, was shown by a 
microscopical examination of the feces. The feces from both the 
entire-wheat and the graham flours under the microscope showed a 
larger proportion of starch particles that had not been acted upon in 
the digestive tract than the feces from standard patent flour. The 
micro-photographs reproduced (Pis. I-III) show the fineness of division 
of the three sorts of flour and the starch granules in the feces obtained 
from the standard patent, the entire-wheat, and the graham flours, 
prepared by grinding in a mortar. 

These deductions are in accord with the results of numerous micro- 
scopical studies of the feces from different sorts of wheat products, and 
in this connection it is interesting to refer to some of these and closely 
related investigations. Among others may be mentioned the work of 
Rubner/' Pappenheim, & Constantinidi/ and Raudnitz. a 

In general it may be said that these investigators found that starch 
was very thoroughly digested, but that the cells making up the outer 
portion of the wheat berry were little attacked by the digestive juices, 
and hence the contents of such cells were not assimilated. Rubner 
pointed out that the amount of undigested nitrogen increased with an 
increase in the amount of the outer portion of the grain retained in 
flour in milling. Rathay e reports experimental studies, of which he 
himself was the subject, in which the diet for a week consisted of 
graham bread and tea. The bread was made without leaven or yeast. 
The feces from the fifth and seventh day were examined microscop- 
ically. He found that the grain portions which had been little masti- 
cated were softened, but almost entirely undigested. From only a 
few of the outer cells of the endosperm had the starch grains and the 
proteid materials disappeared, while the greater part of these nutri- 
ents was excreted unchanged. The general conclusion from his inves- 
tigations was that the greater portion of the feces consisted of undi- 
gested residues of wheat bran in the form of large flakes composed 
of the seed coats and aleurone layer. The latter leaves the intestines 
unchanged, probably because the thick walls of the aleurone cells pre- 
vent the action of digestive juices upon the cell contents. So far as 
can be learned, this investigation was the first which at all satisfac- 



"Ztschr. Biol., 15 (1879), p. 115. 

&Lehrbuch der Miillerei (1890), 3d ed., cited by Moeller. 

cZtschr. Biol., 23 (1887), p. 447. 

tfPrag. med. Wchnschr., 7 (1892), pp. 1, 13. 

e Jahresber. K. K. Realschule Sechshaus, Wien, 1874, cited by Moeller. 




<J. S. Dept. of Agr., Bui. 1 26, Office of Expt. Statior 



Plate I. 




FtG. 1 



-Flour Particles from Straight Patent Flour No. 240 (Magnified 15 
Diameters). 




Fig. 2. -Flour Particles from Entire-wheat Flour No. 241 (Magnified 15 

Diameters). 



U. S. Dept. of Agr., Bui. 126, Office of Expt. Stations. 



Plate II. 




Fig. 1.— Flour Particles from Graham Flour No. 243 (Magnified 15 Diameters). 




Fig. 2.— Feces from Bread Made from Straight Patent Flour (Magnified 15 

Diameters). 



U. S. Dept. of Agr., Bui. 126, Office of Expt. Stations. 



Plate III. 



" V 




m& 



# v 



a 



ss. 



Fig. 1.— Feces from Bread Made from Graham Flour (Magnified 15 Diameters). 




Fig. 2.— Feces from Bread Made from Entire-wheat Flour (Magnified 15 

Diameters). 



49 

torily opposed Liebig's idea of the high value of the gluten layer of 
wheat. 

Perhaps the most extended study of vegetable residues occurring 
in feces was made by Moeller". In some of the experiments the 
diet consisted of coarse bread with, butter and cheese; white bread, 
rice, and butter; bread, and porridge made of wheat grits and milk; 
bread, and porridge made from milk and flour; oat preparations, 
namely, oat grits, oat flake, soup, and oat cocoa; rye bread and various 
mixed diets, or diets in which potatoes or legumes predominated. 
Portions of feces were repeated^ washed with water and then exam- 
ined under the microscope. The conclusion was reached that healthy 
individuals digested the starch of cereals and potatoes almost completely, 
even when the starchy foods were not in favorable mechanical condition, 
as is the case in bran from cereals, in rice, or in sliced potatoes; and fur- 
ther, that the soft cell walls of the starch cells are also digested. The 
aleurone layer of cereals in which the cell membranes consist of pure 
cellulose was not digested, nor were the protein and fat which form 
the contents of the cells digested unless the cell walls had been mechan- 
ically ruptured. The cells making up the germ were not digested or 
ruptured by the action of the digestive juices. The author believes 
that these experiments warrant the conclusion that fine flour is prefer- 
able to coarse flour. Comparative experiments with coarse flour and 
the same flour after passing through the intestinal tract, lead the 
author to the conclusion that the cell walls almost absolutely shield 
the cell contents of the aleurone layer from the action of the digestive 
•juices, and he concludes that cereal brans should be regarded as indi- 
gestible. The outer layer of the cereal grains, including endosperm 
cells with their starch content, was also found to be undigested. 

Laboratoiy experiments indicated that cellulose which had not ligni- 
fied was little attacked by digestive juices, the amount being inversely 
proportional to the thickness of the cell membrane. On the other 
hand, the middle lamellae were readily disintegrated by digestive juices. 
Tests with laboratory reagents also showed that the inner side of the 
gluten cells was most resistant but after a time softened, and this indi- 
cates that possibly gluten cells may become softened in the intestine 
and then digested. That this occurs very seldom is indicated by the 
large number of unchanged cells found in the feces. 

As noted above, in connection with the experiments reported in 
this bulletin, a microscopical examination of the feces showed that 
in those from the graham and entire-wheat breads made from flour 
ground from the same lot of soft wheat, a much larger number of 
unaltered starch granules were present, and the particles had not been 
as completely acted upon by the digestive fluids as in the case of the 
straight-grade-flour bread. 

«Ztschr. Biol., 35 (1897), p. 291. 
19047— No. 126—03 1 



50 

Summarizing briefly the results of the fifteen experiments with soft- 
wheat flours, it appears that while the graham and entire-wheat flours 
contain a larger amount of protein and energy, the lower degree of 
digestibility of these flours, due to the coarser granulation, renders 
available to the body a smaller proportion of total nutrients as well as 
energy than in the case of straight-grade flours, ground from the same 
wheat, which are more finely granulated and more completely digested. 
This is entirely in accord with the results obtained in the investiga- 
tions with hard-wheat flours more exhaustively milled. 

As was the case in the tests with bread from different grades of hard- 
wheat flour, no variations were observed in the metabolism of nitrogen 
which could be attributed to the use of the different sorts of flour 
constituting the principal part of the diet. 

GENERAL SUMMARY OF RESULTS AND CONCLUSIONS. 

The experiments with hard wheat milling products reported in the 
present bulletin are the latest of a fairly extended series which has 
given uniform results. The experiments with soft wheat are the first 
of a proposed series and are less numerous than those made with hard 
wheat. The results already obtained, however, are in accord with 
what has been learned regarding the milling products of hard wheat. 
Some general deductions from the experiments as a whole seem 
warranted. 

. As shown by analysis the patent flour, ground from the hard and 
soft wheats studied, had a somewhat lower protein content than the 
graham flour and entire-wheat flour ground from the same wheats, but 
according to the results of digestion experiments with the different 
grades of flour from these wheats, the proportion of digestible pro- 
tein and the available energy in the patent flour was larger than in 
the coarser grades. The lower digestibility of the protein in the latter 
is, it appears, due to the fact that in these grades a considerable por- 
tion of this constituent is contained in the coarser particles (bran) and 
thus escapes digestion as it is not acted upon by the digestive juices. 
Thus, while there may be actually more protein in a given amount of 
graham or entire-wheat flour than in an equal amount of patent flour 
ground from the same wheat, the body secures less of the protein and 
energy from the coarse flour than it does from the fine, since although 
the retention of the bran and germ increases the percentage of pro- 
tein it decreases the digestibility. By digestibility is meant the dif- 
ference between the amounts of the several nutrients consumed and 
the amounts excreted in the feces. JNo attempt was made to study the 
ease or rapidity of digestion of the different sorts of flour. When the 
digestibility of different grades of patent flour was studied it was 
found that there was no marked difference between standard patent 



51 

flour and the other grades in this respect. The digestibility of all 
these flours was found to be high, apparently owing largely to their 
mechanical condition, that is, owing to the fact that they were finety 
ground. 

Microscopical studies of the feces from bread made from the different 
grades of flour indicate that the superior digestibility of patent-flour 
bread is due to the fineness of division of the flour particles and also to 
the fact that the cell walls of the material making up the interior of 
the wheat berry are less resistant to digestive juices than the walls of 
the cells making up the outer layers of the grain. In other words, the 
patent flour is superior as regards digestibility, on account of both its 
mechanical condition and its physical properties. 

In discussions of the comparative value of fine wheat flour and the 
coarser grades, it is often claimed that the larger proportion of mineral 
matter, and especially phosphorous compounds, in whole -wheat and 
graham flours is a reason for preferring them to patent flour. In this 
case also it is undoubtedly true that the proportion of mineral con- 
stituents which is digestible, or, in other words, which the body can 
retain, from the different sorts of flour, must be considered, as 
well as the amounts which chemical analysis shows to be present in 
the food. In view of the fact that there is apparently no satisfac- 
tory method for determining the proportion of ash in the feces, 
derived from metabolic products, and that it is, therefore, impossible 
by present methods to determine the true digestibility of the mineral 
constituents, no values for the digestibility of ash have been included 
in the present bulletin. It may be noted in this connection that 
it is a well- recognized fact that when the coarser milling products 
are fed to cattle no great amount of phosphorus (one of the most 
important manurial elements) is retained in the animal body. This may 
possibly be an indication that the phosphorus, even if present in con- 
siderable amounts in the feed, is not in a form which can be assimilated 
by animals.. This is, however, little more than conjecture, and more 
experiments with man and the lower animals are needed before satis- 
factory conclusions can be drawn. 

Briefly stated, the most important deductions from the results of 
these investigations with hard and soft wheat are in accord with the 
conclusions drawn from the earlier investigations of this series. The 
nutritive value of flour, in so far as the quantities of digestible protein, 
fats, and carbohydrates, and available energy are concerned, is not 
increased by milling the wheat in such a way as to retain a large pro- 
portion of bran and germ. The differences in the amounts of total 
nutrients furnished the body by the various grades of flour are, how- 
ever, relatively small, all grades being quite thoroughly digested. 
The coarser flours have a tendency to increase peristaltic action, and 
are on this account especially valuable for some persons. Judged by 



52 - £• 

composition and digestibility, all the flours are very nutritious foods, 
which experience has shown are wholesome as well. When also the 
fact is taken into account that they furnish nutritive material in an 
economical form, their importance is evident. The fact must not be 
lost sight of that using different grades of flour for bread making and 
other household purposes offers a convenient method of adding to the 
variety of the daily diet, a matter which is of undoubted importance. 

o 



LEMr'07 



